THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 

LOS  ANGELES 

GIFT  OF 


William  Starke  Rosecrans,!! 


U.S.  DEPARTMENT  OF  AGRICULTURE. 

BUREAU  OF  ANIMAL  INDUSTRY. 


SPECIAL   REPORT 


ON  THE 


RESULTS  OF  EXPERIMENTS 


CONDUCTED  UNDER  THE  DIRECTION  OF  DR.  D.  E.  SALMON, 
CHIEF  OF  THE  BUREAU  OF  ANIMAL  INDUSTRY. 


BY 


THEOBALD  SMITH,  PH.  B.,  M.  D. 


PUBLISHED  BY  AUTHORITY  OF  THE  SECRETARY  OF  AGRICULTURE. 


WASHINGTON: 

GOVERNMENT   PRINTING   OFFICE. 
1891. 


TABLE  OF  CONTENTS. 


Page. 

Letter  of  transmittal 7 

Investigations  concerning  the  nature  and  etiology  of  swine  plague 9 

Introductory 9 

Brief  description  of  the  methods  employed  in  the  investigations 11 

Brief  summary  of  the  earlier  investigations  of  swine  plague  (1886-1888) .    19 

In  Illinois 19 

In  Iowa  (1886) 23 

In  the  District  of  Columbia 23 

In  Maryland 27 

In  Iowa  (1888) 28 

Investigations  of  1889-1890 31 

In  the  District  of  Columbia 31 

In  New  Jersey 57 

Swine-plague  bacteria,  general  characters 85 

Resistance  to  destructive  agents 90 

Pathogenic  action  of  swine-plague  bacteria 93 

Effect  on  small  animals 93 

The  disease  in  swine  as  produced  by  the  inoculation  of  cultures 97 

Swine  plague  as  observed  in  epizootics .- 98 

Disease  of  the  digestive  tract  in  swine  plague 102 

Attenuated  swine-plague  bacteria  in  sporadic  cases  of  pneumonia,  in  septic 
diseases  of  swine,  and  in  the  upper  air  passages  of  healthy  swine  and  other 

domesticated  animals 109 

Other  investigations  of  swine  plague 118 

American ,. 118 

European 125 

Practical  observations 133 

1.  Conditions  which  may  favor  and  oppose  outbreaks 133 

2.  Distribution  and  transmission  of  swine-plague  bacteria 135 

3.  Relation  of  hog  cholera  to  swine  plague 138 

4.  Relation  of  swine  plague  to  diseases  of  other  domesticated  animals 141 

5.  Measures  to  be  taken  in  the  prevention  of  swine  plague 145 

Conclusions 149 

Appendix. — The  presence  of  septic  bacteria  probably  identical  with  those  of 

swine  plague  in  the  upper  air  passages  of  domestic  animals  other  than 

swine,  by  Dr.  V.  A.  Moore 151 

Description  of  plates 161 

3 


932484 


LIST  OF  ILLUSTRATIONS. 


Page. 

PLATE  I.  Normal  lungs  of  pig,  inflated,  lateral  surface 163 

II.  Same  lungs,  diaphragmatic  surface 163 

III.  Hepatization  of  lung  with  pleuritic  exudate 163 

IV.  Same  lung  with  adherent  portion  of  diaphragm 163 

V.  Hepatization  of  lung  with  necrotic  foci 163 

VI.  Pneumonia,  pleuritis,  and  pericarditis  produced  by  inoculation  of 

swine-plague  bacteria 163 

VII.  Caseous  degeneration  of  lungs  in  swine  plague 163 

VIII.  Caseous  masses  in  lung  tissue.     Masses  of  exudate  in  large  intestine.  163 

IX.  Collapse  and  broncho-pneumonia 163 

X.  Pericarditis  in  swine  plague 163 

XL  Swine-plague  bacteria  (highly  magnified) 163 

XII.  Swine-plague  bacteria  in  cultures w 163 

6 


LETTER  OF  TRANSMITTAL 


WASHINGTON,  D.  C.,  July  20, 1891. 

SIB  :  I  have  the  honor  to  submit  herewith  the  second  special  report 
upon  the  investigations  of  infectious  swine  diseases.  The  first  report 
dealt  mainly  with  hog  cholera,  while  the  accompanying  report  is  de- 
voted to  swine  plague. 

In  this  volume  the  investigations  are  reported  in  detail  which  have 
led  up  to  a  separation  of  swine  plague  as  an  independent  disease  from 
hog  cholera.  The  difficulties  surrounding  investigations  of  infectious 
swine  diseases  have  been  very  much  increased  by  the  frequent  associa- 
tion of  both  hog  cholera  and  swine  plague  in  the  same  herd.  This 
has  necessitated  frequent  repetitions  of  investigations  before  positive 
results  could  be  obtained. 

The  importance  of  thoroughly  scientific  investigations  of  infectious 
animal  diseases  is  becoming  more  and  more  apparent,  and,  owing 
to  the  commercial  interests  at  stake,  the  subject  is  now  assuming  an 
international  character.  Even  though  investigations  of  this  nature 
do  not  at  once  suggest  the  means  of  dealing  satisfactorily  with  such 
diseases,  it  is,  nevertheless,  essential  that  we  should  know  as  much  as 
possible  of  the  nature  of  every  one  of  them  within  our  boundaries  if 
we  expect  to  bring  to  bear  upon  them  all  the  knowledge  which  is 
accumulating  so  rapidly  in  various  parts  of  the  civilized  world.  The 
investigations  in  this  report  prove  the  existence  of  a  virulent  swine 
disease  due  to  specific  bacteria  and  its  identity  with  the  disease  of 
Scliweineseuclie,  prevalent  in  Germany.  It  also  demonstrates  the  wide 
distribution  of  this  class  of  bacteria,  chiefly  as  varieties  of  feeble 
disease-producing  power  in  the  upper  air  passages  of  various  domesti- 
cated animals.  It  is  not  improbable  that  this  group  of  bacteria  may, 
when  exceptionally  virulent,  attack  other  domesticated  animals,  and 
indeed  we  know  that  the  bacteria  of  at  least  one  form  of  fowl  cholera 
can  not  be  distinguished  from  those  of  swine  plague  by  the  bacterio- 
logical methods  now  in  use.  In  short,  this  group  of  bacteria  which 
appears  to  have  a  world-wide  distribution,  may  be  considered  as  very 
dangerous  to  our  domesticated  animals,  and,  consequently,  the  care 
with  which  they  have  been  studied,  more  particularly  with  reference 
to  their  disease-producing  properties,  is  fully  justified. 

With  the  publication  of  this  and  the  preceding  volume  the  informa- 
tion is  given  by  which  a  diagnosis  can  be  made  of  the  two  principal 

7 


8 

infectious  diseases  to  which  our  swine  aj-e  subject.  The  nature  and 
cause  of  these  diseases  are  made  clear,  and  knowing  these,  we  can 
apply  the  curative  and  preventive  measures  which  the  progress  of 
medical  science  has  made  possible,  or  which  future  researches  may 
show  to  be  available. 

D.  E.  SALMON, 

Chief  of  the  Bureau  of  Animal  Industry. 
Hon.  J.  M.  RUSK, 

Secretary  of  Agriculture. 


INVESTIGATIONS  CONCERNING  THE  NATURE  AND  ETIOLOGY 
OF  SWINE  PLAGUE. 


INTRODUCTORY. 

Since  1886  the  bacteriological  investigations  carried  on  in  the  labora- 
tory of  the  Bureau  of  Animal  Industry  on  infectious  swine  diseases 
have  revealed  the  existence  of  pathogenic  bacteria  differing  markedly 
from  those  causing  hog  cholera.  They  preferably  attack  the  chest 
organs  of  swine,  the  lungs,  and  serous  membranes  covering  these  vital 
organs.  The  difficulty  encountered  from  the  beginning  in  obtaining  a 
clear  understanding  of  the  action  of  these  disease  germs  is  the  frequent 
mingling  of  hog  cholera  with  this  disease,  which  has  been  called  swine 
plague.  In  some  outbreaks  only  hog-cholera  bacilli  are  detected,  in 
others  only  swine-plague  bacteria,  while  in  the  majority  of  outbreaks 
thus  far  studied  both  bacteria  are  associated  together.  This  condition 
is  very  likely  due  to  their  wide  distribution  over  the  country. 

The  importance  of  swine  plague  bacteria  is  not  limited  to  swine  dis- 
eases alone,  for  they  belong  to  a  group  of  bacteria  which  in  various 
parts  of  the  world  have  attacked  other  species,  such  as  cattle,  horses, 
game,  and  fowls,  and  the  question  whether  there  may  not  be  a  trans- 
mission of  such  diseases  from  one  species  of  farm  animals  to  another 
must  not  be  lost  sight  of. 

The  swine-plague  bacteria  have  been  very  carefully  studied  in  view 
of  their  importance,  and  attention  has  been  given  more  directly  to  their 
pathogenic  effect  on  the  smaller  experimental  animals,  such  as  mice, 
rabbits,  guinea-pigs,  pigeons,  and  fowls,  in  order  that  a  proper  tinder- 
standing  of  their  relative  virulence  could  be  obtained.  Investigations 
in  various  diseases  have  brought  to  light  bacteria  which,  although  iden- 
tical so  far  as  we  are  able  to  determine,  vary  greatly  in  their  virulence, 
and  it  seems  now  that  the  relative  virulence  or  disease-producing  power 
must  be  looked  upon  as  the  chief  criterion  of  danger.  Feeble  virulence 
signifies  a  feebly  infectious  localized  disease.  A  high  degree  of  viru- 
lence signifies  the  power  to  spread  and  perhaps  to  attack  other  species. 
This  important  factor  of  virulence  can  only  be  measured  by  the  inocula- 
tion of  animals  of  various  degrees  of  susceptibility.  The  great  variation 
in  the  virulence  of  both  swine-plague  and  hog-cholera  bacilli  has  been 
demonstrated  in  this  way,  and  when  we  come  down  to  the  lowest  grades 

9 


10 

tbe  problem  arises,  can  such  varieties  produce  disease  at  all,  and  are 
they  not  merely  accidentally  present  ?  An  answer  to  this  question  can 
not  be  given  categorically  at  present,  and  its  solution  will  demand  con- 
tinued, undivided  attention  to  this  subject  of  disease  germs  for  some 
time  to  come. 

Another  fact,  the  significance  of  which  has  been  discussed  in  the 
text,  is  the  existence  of  bacteria  in  the  air  passages  of  various  domesti- 
cated animals  during  health,  which  are  not  distinguishable  from  swine- 
plague  bacteria  excepting  by  feebler  pathogenic  effect. 

The  question  whether  swine  plague  is  an  infectious  disease  by  itself, 
demanding  the  attention  of  the  veterinarian,  the  agriculturist,  and  the 
Government,  was  practically  solved,  though  not  absolutely  demon- 
strated, by  the  investigations  of  1887.  The  repeated  attacks  upon  this 
work  made  it  desirable  to  spend  much  more  time  than  was  actually 
necessary  in  the  investigation  of  outbreaks  as  they  came  within  reach 
of  facilities  from  time  to  time,  and  now  a  large  amount  of  material  has 
been  collected  which  fully  confirms  the  position  taken  in  1887,  that 
there  are  at  least  two  swine  diseases  of  an  infectious  character.  These 
have  very  likely  existed  together  for  a  long  time,  but  a  differentiation 
could  only  be  effected  by  the  advanced  position  of  bacteriology  and  the 
ample  means  provided  by  the  Government. 

The  frequent  association  of  hog-cholera  bacilli  with  swine-plague 
bacteria  has  made  it  necessary  to  pay  some  attention  to  hog  cholera  as 
well.  These  investigations  are  based  on  the  facts  already  published 
on  hog  cholera  and  the  bacillus  of  that  disease  in  the  special  report  on 
hog  cholera  (1889).  This  report  is  therefore  necessary  to  an  under- 
standing of  the  contents  of  the  present  volume  so  far  as  the  strictly 
experimental  portion  is  concerned. 

It  is  to  be  hoped  that  these  investigations  will  prove  not  only  of  ad- 
vantage in  the  protection  of  swine  from  disease,  but  will  be  a  basis  for 
the  investigation  of  diseases  of  other  domesticated  animals  due  to  this 
group  of  bacteria,  which  may  appear  at  any  time  owing  to  the  growing 
complexity  of  intercourse  between  different  sections  of  the  country, 
modifications  in  the  methods  of  stock-raising,  etc. 

It  must  not  be  assumed  that  our  knowledge  of  the  etiology  of  swine 
diseases  is  complete  even  with  the  advances  made  thus  far  in  swine 
plague  and  hog  cholera.  There  are  important  questions  with  reference 
to  both  diseases  which  demand  elucidation.  Especially  is  it  desirable 
to  investigate  those  outbreaks  more  carefully  in  which  we  find  the  ap- 
pearances of  hog  cholera  without  the  bacilli  in  the  internal  organs. 
The  complete  mastery  over  a  disease  is  only  to  be  obtained  by  complete 
insight  into  its  causes.  If  all  the  suggestions  derived  from  scientific  in- 
vestigations, conscientiously  applied,  fail  to  prevent  the  appearance  of 
a  given  disease  it  signifies  that  our  information  is  as  yet  incomplete, 
and  that  there  are  some  still  unknown  channels  through  which  the 
bacteria  of  such  disease  are  distributed. 


11 

To  devise  a  proper  plan  for  an  intelligible  presentation  of  the  inves- 
tigations and  results  which  will  be  satisfactory  to  those  who  are  not 
immediately  interested  in  the  investigations,  and  simply  desire  to  know 
the  deductions  so  as  to  be  guided  by  them,  has  been  a  difficult  one,  and 
has  demanded  the  occasional  repetition  of  statements.  In  general  all 
those  facts  not  necessary  to  an  understanding  of  the  text  have  been  put 
into  smaller  type.  All  the  investigations  proper,  including  a  detailed 
description  of  the  various  outbreaks,  autopsy  and  bacteriological  notes, 
test  inoculations  of  swine  and  smaller  animals,  have  been  kept  together 
under  the  respective  outbreaks,  while  all  essential  information  derived 
from  these  investigations  and  experiments  is  to  be  found  in  the  subse- 
quent sections  of  the  report. 

The  contents,  therefore,  have  been  arranged  in  the  following  order : 

The  methods  of  work  are  first  described,  followed  by  a  brief  review  of 
earlier  and  a  more  detailed  account  of  later  investigations.  Then  come 
a  general  description  of  the  swine-plague  bacteria,  of  their  disease-pro- 
ducing power,  and  some  facts  showing  the  wide  distribution  of  this 
group  of  bacteria  among  domesticated  animals  in  a  healthy  condition. 
A  chapter  is  also  added,  giving  a  brief  account  of  the  investigation  of 
others  in  this  field.  Lastly,  all  the  results  and  practical  observations 
which  may  be  of  value  to  the  farmer  are  brought  together. 

The  writer  acknowledges  the  continued  assistance  since  1886  of  Dr. 
F.  L.  Kilborne,  veterinarian  of  the  Experiment  Station,  who  has  had 
charge  of  the  experimental  animals,  has  assisted  in  many  of  the  post 
mortem  examinations,  and  has  perform  ed  the  inoculations  upon  swine. 
In  the  laboratory,  Dr.  V.  A.  Moore  has  assisted,  since  1888,  in  general 
pathological  and  bacteriological  work.  The  special  services  of  these 
gentlemen  are  also  referred  to  in  the  text. 

BRIEF  DESCRIPTION   OF  THE   METHODS    EMPLOYED  IN  THE  INVESTI- 
GATIONS. 

The  difficulties  that  are  met  with  in  the  investigation  of  infectious 
swine  diseases  are  not  those  usually  encountered  in  bacteriological  in- 
vestigations. In  the  first  plaee  outbreaks  occur  as  a  rule  some  distance 
from  a  laboratory.  Yet  the  amount  of  bacteriological  work  demanded 
by  each  case,  in  order  that  any  conclusion  may  be  reached,  can  not  be 
done  excepting  in  a  well  equipped  laboratory.  Hence  it  has  been  our 
effort  to  transfer,  if  possible,  cases  of  the  disease  to  the  Experiment 
Station,  and  also  to  keep  up  the  disease  there  by  exposing  fresh  cases. 
In  fact,  only  those  investigations  carried  on  in  this  way  can  be  regarded 
as  complete,  while  cultivations  made  in  the  field  are  at  best  restricted 
to  a  few  or  only  one  organ,  and  plate  cultures  are  out  of  the  question. 

Another  difficulty  is  due  to  the  belated  information  which  we  obtain 
of  any  given  outbreak.  Usually  from  one-third  to  two-thirds  of  the 
herd  have  perished  before  the  investigations  are  begun.  This  is  unfor- 
tunate in  swine  plague,  because  the  earliest  cases  are  the  most  satis- 


12 

factory  from  a  bacteriological  standpoint,  since  the  swine-plague  bacteria 
are  most  easily  demonstrated  in  such  cases.  It  seems  that  the  infection 
passes  through  a  herd  quite  rapidly,  and  those  animals  which  live  long- 
est have  reached  a  stage  of  the  disease  in  which  the  swine-plague 
bacteria  may  have  entirely  disappeared. 

A  third  difficulty  to  be  contended  with  is  the  rapid  death  of  the  ani- 
mals, which  makes  a  thorough  examination  of  each  animal  impossible. 
The  alternative  before  us  is  either  to  limit  our  examination  to  a  certain 
number  of  organs  in  every  animal,  or  else  to  examine  a  few  very 
thoroughly.  While  we  have  endeavored  to  meet  both  demands,  of  ex- 
amining every  animal,  and  also  doing  it  as  thoroughly  as  possible,  we 
have  but  partially  succeeded  in  this,  owing  to  lack  of  facilities  and 
assistance.  The  pathological  changes  differ  so  much  from  animal  to 
animal,  the  extent  of  the  organs  involved  varies  to  such  a  degree,  that 
there  is  a  great  temptation  to  examine  every  animal  in  the  hope  that 
most  information  can  be  obtained  in  this  way. 

The  investigations  consisted  in  watching  the  course  of  the  disease  in 
the  infected  animals,  in  post-mortem  examinations  of  those  that  died, 
in  microscopic  examination  of  the  diseased  tissues,  fresh  and  hardened, 
and  in  bacteriological  examination  of  a  certain  number  of  organs.  The 
post-mortem  examination  included  the  various  organs  and  tissues,  with 
the  exception  of  the  brain  and  spinal  cord,  which  were  exposed  in  a 
very  few  cases  only.  The  skin  was  first  reflected  from  the  thorax  and 
abdomen,  the  abdomen  carefully  opened,  and  the  spleen  or  a  portion  of 
it  first  removed  with  sterile  instruments  and  reserved  for  further  ex- 
amination. From  any  fluid  or  exudate  present  a  minute  quantity  was 
transferred  to  culture  media  by  means  of  a  platinum  wire  bent  into 
a  loop  about  three  to  four  millimetres  in  diameter  and  soldered  into  a 
glass  rod.  The  thorax  was  next  opened  by  removing  the  sternum,  and 
from  any  effusion  or  exudate  cultures  were  made  at  once.  The  vari- 
ous organs  destined  to  be  used  for  bacteriological  examination  were 
removed  in  whole  or  in  part  before  being  soiled. 

Portions  of  organs  designed  for  microscopical  examination  were  in 
part  examined  fresh  by  making  sections  with  the  razor,  teasing,  etc., 
in  part  hardened  in  95  per  cent,  alcohol  and  infiltrated  with  paraffin 
before  the  sections  were  made.  These  were  stained  in  different  ways, 
chiefly  in  alum  carmine  and  in  alkaline  methylene  blue  (Loffler),  which 
was  found  most  satisfactory  in  bringing  out  the  swine- plague  bacteria. 

The  various  cultures  were  made  in  the  following  manner:  With  a 
platinum  spatula  a  small  area  of  the  surface  of  an  organ  was  thoroughly 
scorched,  and  from  the  scorched  area  minute  particles  of  tissue  were 
cut  out  with  flamed  scissors  and  forceps,  the  scorched  layer  being 
rejected.  These  particles  were  then  transferred  to  various  media  for 
tube  and  plate  cultures  and  also  used  for  the  inoculation  of  animals. 
Another  mode  of  inoculating  cultures  used  was  to  pierce  the  scorched 
area  with  a  straight  stiff  platinum  wire,  which  was  then  stirred  about 


13 

in  liquefied  media  or  rubbed  over  the  surface  of  agar.  In  this  way 
only  a  minute  trace  of  the  parenchyma  could  be  transferred,  and  it 
was  only  used  when  bacteria  were  numerous  enough  to  be  detected 
under  the  microscope.  In  the  notes  given  with  the  various  outbreaks 
the  platinum  loop  and  wire  mean  respectively  the  looped  wire  and  the 
straight  wire.  Note  is  merely  made  of  this  to  indicate  the  difference  in 
the  quantity  of  material  used  to  inoculate  the  culture  media. 

The  more  usual  method  in  vogue  of  disinfecting  the  external  surface 
of  organs  by  placing  them  in  a  5  per  cent,  solution  of  .carbolic  acid  or 
a  one-tenth  per  cent,  solution  of  mercuric  chloride  for  a  short  time, 
then  making  several  incisions  in  planes  at  right  angles  to  one  another 
into  the  depth  of  the  organ,  was  not  employed,  because  the  method 
already  mentioned  of  scorching  a  small  portion  of  the  surface  seemed 
safer  and  more  satisfactory.  When  cultures  were  inoculated  with 
blood  this  was  done  from  the  right  ventricle  while  the  heart  was  still 
in  situ.  The  thin  ventricular  wall  was  scorched  over  a  small  area, 
then  the  edge  of  the  spatula  was  used  to  burn  through.  The  platinum 
wire  or  loop,  or  the  glass  pipette,  if  blood  was  to  be  collected,  was 
inserted  through  the  hole  thus  made.  The  same  methods  were  employed 
in  the  examination  of  the  small  experimental  animals. 

For  the  cultivation  of  swine-plague  bacteria  agar-agar  as  usually 
prepared  with  bouillon,  peptone,  and  common  salt,  and  the  ordinary 
peptone  bouillon,  are  the  best  media.  In  the  earlier  investigations 
nutrient  gelatine  was  chiefly  employed,  but  it  was  found  that  some 
varieties  of  swine-plague  bacteria  may  refuse  to  multiply  in  it,  hence 
it  was  discarded.  In  addition  to  plate  cultures  for  the  isolation  of  these 
bacteria  the  inclined  surface  of  agar  in  tubes  is  of  great  service.  In 
many  cultures  the  colonies  appeared  completely  isolated  on  the  agar 
surface,  thus  enabling  us  to  start  from  single  colonies  when  plate  cul- 
tures had  not  been  prepared  at  the  same  time. 

For  the  inoculation  of  smaller  animals  with  bacteria  from  cultures 
two  methods  were  employed :  (1)  A  small  pocket  was  made  in  the  sub- 
cutis  by  an  incision  through  the  skin  with  sterilized  scissors  and  a  loop 
of  the  growth  rubbed  into  this  pocket ;  (2)  liquid  cultures  were  pre- 
pared by  inoculating  peptone  bouillon  and  allowing  the  liquid  to  become 
clouded  in  the  thermostat  or  by  transferring  the  growth  from  agar 
tubes  into  sterile  bouillon  or  water  and  making  a  suspension.  The 
liquid  was  then  injected  with  a  hypodermic  syringe  into  the  sub- 
cutaneous tissue  or  into  a  vein.  The  hypodermic  syringes  used  were  of 
the  ordinary  pattern,  since  the  various  others  devised,  such  as  the  Koch 
syringe  and  the  asbestos-packed  syringe,  were  found  leaky  and  ineffi- 
cient and  did  not  enable  us  to  inject  a  definite  quantity  with  accuracy. 
In  this  investigation  these  syringes  could  the  more  easily  be  dispensed 
with,  since  both  swine-plague  and  hog-cholera  bacteria  are  sporeless  and 
killed  by  disinfectants  in  very  dilute  solutions.  The  syringes  and 
needles  were  disinfected  both  before  and  after  use  by  filling  them  with 


14 

5  per  cent,  carbolic  acid  and  allowing  this  to  remain  for  15  or  20  minutes. 
The  acid  was  then  removed  with  boiling  water.  Great  care  was  taken 
that  no  fluid  passed  beyond  the  piston.  If  it  did  the  syringe  was  taken 
apart  and  the  parts  immersed  in  5  per  cent,  carbolic  acid.  While  this 
method  of  making  injections  may  seem  theoretically  objectionable,  it 
has  nevertheless  at  no  time  proved  the  source  of  any  accidental  infec- 
tion. This  method  is  not  applicable,  however,  to  bacteria  which  pro- 
duce spores,  or  which  prove  very  resistant  to  disinfectants,  such  as 
anthrax  and  tuberculosis.  In  general  syringes  were  dispensed  with 
and  the  first  method  employed  when  the  accurate  measurement  of  the 
quantity  of  virus  to  be  injected  was  not  essential. 

The  technical  difficulties  surrounding  the  problem  of  the  causation 
of  swine  diseases  are  mainly  due  to  the  intermingling  of  two  diseases, 
hog  cholera  and  swine  plague.  As  this  problem  will  be  discussed  fur- 
ther on,  only  those  points  need  be  considered  here  which  involve  the 
methods  employed.  The  important  question  to  be  decided  in  every 
outbreak  is  whether  one  or  both  kinds  of  bacteria  are  present.  This 
can  only  be  determined  by  bacteriological  investigation.  It  is  evident 
that  to  examine  every  organ  of  every  pig  bacteriologically  is  a  task  of 
enormous  dimensions,  hence  the  simplest  reliable  method  must  be  em- 
ployed. At  first  thought  it  would  seem  sufficient  to  make  plate  cultures 
from  the  various  organs  and  examine  the  colonies  as  they  develop. 
There  are,  however,  objections  to  this  method  taken  alone.  Certain 
varieties  of  swine  plague  bacteria,  especially  the  most  virulent,  do  not 
as  a  rule  grow  in  gelatine,  while  on  agar  the  colonies  of  hog  cholera  can 
not  be  distinguished  positively  from  those  of  swine  plague,  unless  the 
bacteria  composing  these  colonies  are  examined.  For  a  rapid  and  reli- 
able determination  of  the  presence  or  absence  of  these  two  kinds  of 
bacteria,  1  have  found  in  addition  agar  and  bouillon  tube  cultures  nec- 
essary. The  motile  hog  cholera  bacilli  are  detected  at  once  in  the 
bouillon  and  in  the  condensation  water  of  the  inclined  agar  cultures. 
Such  cultures  may  then  be  plated,  and  fresh  cultures  of  the  hog-cholera 
bacilli  and  the  swine-plague  bacteria  obtained  by  inoculating  from 
isolated  colonies.  These  cultures  are  then  in  condition  to  be  tested  on 
smaller  animals  to  make  the  diagnosis  complete.  While  it  is  desirable 
that  when  both  kinds  of  bacteria  are  present  they  should  be  isolated 
from  as  many  animals  as  possible,  it  is  obvious  that  the  presence  of 
virulent  hog-cholera  bacilli  in  a  single  animal  of  a  herd  leads  to  the 
inference  that  they  are  most  likely  present  in  all  the  remaining  diseased 
animals. 

The  detection  of  swine-plague  bacteria  in  liquid  cultures  containing 
hog-cholera  bacilli  is,  as  a  rule,  not  difficult.  The  best  method  consists 
in  the  examination  of  the  liquid  unstained  in  a  drop  suspended  from 
the  under  surface  of  a  cover-glass  resting  on  the  margins  of  a  cell  on 
or  in  the  slide.  The  most  convenient  cell  I  have  found  to  be  a  thin 
glass  ring  fastened  to  the  slide  with  Canada  balsam.  A  little  glycerin 


15 

is  placed  on  the  ring  so  that  when  the  cover  glass  with  the  drop  on  it 
is  inverted  and  laid  on  the  ring  the  immersion  lens  will  not  draw  it  up. 

The  hog-cholera  bacilli  are  readily  detected  in  this  drop  by  their 
motion.*  If  the  border  of  the  drop  be  examined,  the  two  kinds  of  bac- 
teria may  then  be  distinguished  by  a  slight  difference  in  size  in  favor 
of  the  hog-cholera  bacilli.  When  the  growth  from  the  condensation 
water  of  agar  cultures  is  to  be  examined,  it  must  be  diluted  with  bouil- 
lon or  sterile  water  kept  preferably  in  tubes,  just  as  the  bouillon  is,  in 
small  quantities.  The  examination  of  cultures  in  this  manner  can  not 
be  dispensed  with  in  the  study  of  these  diseases.  When  the  presence 
of  one  or  both  kinds  of  bacteria  has  been  positively  determined,  I  find 
staining  of  very  little  value  in  subsequent  work  and  simply  examine 
fluids  as  described.  When  colonies  are  to  be  examined  a  drop  of  bouil- 
lon or  water  in  which  a  trace  of  growth  is  stirred  up  is,  of  course,  nec- 
essary. 

Another  advantage  of  the  bouillon  and  the  condensation  water  of  agar 
tubes  rests  upon  the  fact  that  motile  bacteria  do  not  always  become 
active  at  once  when  transferred  from  agar  or  gelatine  into  liquids  for 
microscopical  examination.  Hence  their  motilitymay  be  entirely  over- 
looked unless  they  are  examined  after  having  multiplied  in  liquids  for 
some  hours  at  least. 

It  should  likewise  be  borne  in  mind  that  the  colonies  of  a  few  bacteria 
in  a  bit  of  tissue  or  drop  of  effusion  from  the  diseased  body  may  escape 
attention  on  a  plate  when  many  other  colonies  are  present ,  and  that 
they  may  be  entirely  lost  on  the  second  or  third  plate.  In  bouillon, 
however,  both  kinds  of  bacteria  have  for  a  time  the  same  opportunities 
for  multiplication,  and  both  may  be  detected  on  the  following  day, 
though  there  may  have  been  originally  a  great  difference  in  the  num- 
bers introduced.  While  agar  plates  have  occasionally  failed  to  dem- 
onstrate the  presence  of  certain  bacteria,  owing  either  to  a  failure  to 
multiply  or  to  the  rapid  growth  of  other  bacteria,  or  to  rapid  drying  out 
of  the  agar  layer,  bouillon  and  agar  tube  cultures  made  at  the  same 
time  have  furnished  the  desired  information. 

In  order  to  detect  both  kinds  of  bacteria  it  is  therefore  essential  that 
bouillon  and  inclined  agar  in  tubes  be  used  with  agar  plates.  The 
method  pursued  in  the  investigations  detailed  in  full  in  this  report  was 
always  to  prepare  plates  from  lungs.  When  there  was  no  time  for  the 
preparation  of  plates  from  other  organs,  such  as  spleen,  liver,  and  kid- 
neys, tubes  of  bouillon  and  agar  were  used  in  place  of  them,  and,  if 
necessary,  plates  were  prepared  from  these. 

A  minor  difficulty,  but  one  which  may  prove  of  more  serious  conse- 
quence to  beginners,  is  the  frequent  encountering  of  bacteria  other 
than  those  producing  the  disease  in  the  organs  of  diseased  swine.  A 
perusal  of  the  bacteriological  observations  in  this  report  will  show  how 
much  time  has  to  be  spent  in  isolating  these  bacteria  and  deterinin- 

*  See  Special  Report  ou  Hog  Cholera,  1889,  for  the  characters  of  these  bacilli. 


16 

ing  what  relation  they  bear  to  the  disease.  Many  of  them  can  event- 
ually be  traced  to  the  intestines  where  they  commonly  vegetate.  Their 
presence  in  the  internal  organs  may  be  accounted  for  by  the  extensive 
lesions  in  lungs  and  intestines  which  serve  as  entrances  into  the  blood. 
This  presence  of  strange  bacteria  has  also  been  observed  in  other  infec- 
tious diseases  by  other  observers,  and  attention  has  been  called  to  it  in 
connection  with  hog  cholera  in  the  special  report  on  that  malady,  p.  58. 

The  detection  of  these  foreign  bacteria  has  been  in  large  part  due  to 
the  use  of  bouillon.  As  they  are  usually  present  in  very  small  numbers 
their  colonies  on  plates  might  easily  be  overlooked  or  attributed  to 
accidental  infection.  They  would  appear  only  on  the  first  plate  among 
large  numbers  of  other  colonies  and  most  likely  be  overlooked,  since 
the  development  of  colonies  on  crowded  plates  is  limited,  and  they  fre- 
quently fail  to  show  any  special  features  unless  they  have  time  and 
opportunity  to  expand.  This  is  true  of  gelatine  and  particularly  so  of 
agar,  on  which  colonies  show,  at  best,  few  differences.  When  bouillon 
is  inoculated  all  bacteria  have  for  a  time  equal  opportunities  to  develop, 
as  stated  above,  and  they  at  once  thrust  themselves  upon  our  attention. 
Such  mixed  cultures  have  been  and  are  still  styled  contaminated  by 
those  who  fail  to  see  their  real  significance.  Such  criticisms  may, 
however,  be  safely  left  to  take  care  of  themselves  at  the  present  time. 

As  an  illustration  of  the  foregoing,  I  have  frequently  found  in  the  bot- 
tom of  bouillon  tubes  into  which  a  bit  of  tissue  had  been  introduced 
large  spore-bearing  bacilli,  which  have  been  referred  to  in  the  various 
reports  as  "anaerobic,"  "post-mortem"  bacilli.  These  bacilli  do  not 
develop  in  fresh  cultures,  nor  would  they  appear  on  plates.  The  bot- 
tom of  the  culture  liquid  and  the  bit  of  tissue  furnish  for  the  time  a 
suitable  soil.* 

The  use  of  animals  in  the  isolation  of  bacteria  is  of  great  value  in 
swine  diseases.  Rabbits  are  peculiarly  susceptible  to  swine-plague  bac- 
teria. Inoculated  with  the  more  virulent  varieties  they  die  within  20 
hours,  and  the  inoculated  bacteria  can  be  obtained  from  the  various 
organs.  Frequently  when  cultures  failed  to  determine  the  presence  of 
these  bacteria  in  tissues  rabbit  inoculation  was  still  successful.  When 
a  mixed  outbreak  is  under  examination  it  is  evident  that  since  rabbits 
do  not  succumb  to  minute  doses  of  hog-cholera  bacilli  in  less  than  7 
days,  the  rabbits  will  die  of  swine  plague  first  and  the  hog-cholera 
bacilli  will  not  be  obtained  from  their  organs.  There  are,  however,  at- 
tenuated varieties  of  swine-plague  bacteria  frequently  encountered  in 
mixed  outbreaks  which  prove  fatal  to  rabbits  in  from  3  to  10  days.  In 
these  cases  when  pure  cultures  are  inoculated  there  is  more  or  less  sup- 
purative  destruction  of  the  subcutis  starting  from  the  point  of  inoc- 
ulation, while  the  internal  organs  are  quite  free  from  changes  and 
bacteria  also.  In  such  protracted  cases,  provided  both  kinds  of  bacte- 

*  For  a  simple  method  of  cultivating  such  bacteria  in  addition  to  those  now  in  use 
for  anaerobes,  see  foot-note,  p.  81. 


17 

ria  were  originally  present  in  the  tissue  inoculated,  both  kinds  may  ap- 
pear in  the  rabbit  cultures,  or  only  the  hog-cholera  bacilli  may  have 
become  disseminated  through  the  body,  while  the  swiue-plague  bacteria 
may  be  limited  to  the  inoculated  locality.  Since  hog-cholera  bacilli  do 
not  produce  much  local  inflammation,  whenever  this  is  extensive  in 
rabbits  inoculated  directly  from  the  pig,  it  is  pretty  certain  that  swine- 
plague  bacteria  and  perhaps  other  still  unknown  bacteria  may  have 
caused  it  and  should  be  looked  for. 

Babbit  inoculation  may  thus  prove  very  serviceable,  but  the  post' 
mortem  appearances  must  be  carefully  interpreted  in  connection  with 
the  bacteriological  observations.  In  any  case  they  rarely  bring  to  light 
hog-cholera  bacilli  when  the  inoculated  animal  succumbs  to  swine  plague 
before  the  fourth  or  fifth  day.  . 

A  few  words  are  necessary  to  define  some  of  the  anatomical  terms 
used  in  the  autopsy  notes,  inasmuch  as  a  thorough  description  of  the 
visceral  anatomy  of  the  domesticated  animals  has  not  yet  been  made. 
Since  the  lesions  are  confined  chiefly  to  the  lungs  and  intestines  our 
remarks  will  be  confined  to  these  organs. 

When  inflated  through  the  trachea  after  thesternum  is  removed,  and  whilethe  lungs 
arc  still  in  their  natural  position  in  the  thoracic  cavity,  it  will  be  observed  that  the 
surface  resting  against  the  ribs  laterally  is  the  most  extensive.  That  surface  rest- 
ing upon  the  diaphragm  comes  next,  while  the  ventral  aspect  is  the  smallest.  (See 
Plates  i,  n.)  The  right  lung  is  made  up  of  four  lobes,  the  left  has  only  three.  (In 
text-books  on  anatomy  the  left  lung  is  considered  as  being  made  up  of  only  two.) 

In  both  there  is  a  large  principal  lobe  resting  upon  the  diaphragm  and  against  the 
adjacent  thoracic  wall.  This  lobe  forms  the  major  part  of  each  lung.  The  remainder, 
occupying  the  anterior  (or  cephalic)  portion  of  the  cavity,  is  made  up  of  two  small 
lobes,  one  extending  ventrally  (or  downward  in  the  standing  position  of  the  animal) 
and  in  the  expanded  state  covering  the  heart  laterally,  the  other  extending  towards 
the  head  and  overlapping  the  base  of  the  heart.  These  small  lobes  may  be  denomi- 
nated the  ventral  and  cephalic  lobes,  respectively.  The  right  cephalic  lobe  is  longer 
and  more  distinct  from  the  ventral  lobe  than  the  corresponding  left  cephalic. 
Wedged  in  between  the  two  principal  lobes  and  resting  on  the  diaphragm  is  a  small 
lobe,  pyramidal,  belonging  to  the  right  lung  (azygos  or  median  lobe).  This  lobe  rests 
on  the  left,  against  the  mediastinal  membrane,  and  on  the  right  it  is  separated  from 
the  right  principal  lobe  by  a  fold  of  the  pleura  passing  from  the  ventral  thoracic  wall 
to  inclose  the  inferior  vena  cava.  This  small  lobe  is  almost  completely  shut  off,  there- 
fore, from  the  other  lobes  by  folds  of  the  pleura. 

When  the  trachea  and  its  branches  have  been  examined  it  is  easier  to  understand 
this  division  into  lobes.  The  trachea  divides  in  the  thorax  into  two  principal 
branches  or  bronchi.  These  bronchi  pass  into  the  principal  lobes,  straight  to 
the  caudal  border,  giving  off  a  number  of  small  branches  along  their  course.  Very 
near  the  place  of  bifurcation  the  left  bronchus  gives  off  a  large  branch,  which  rami- 
fies in  the  substance  of  the  left  ventral  lobe.  From  this  branch  another  goes  to  the 
cephalic  lobe.  In  some  lungs  the  branches  of  these  two  lobes  arise  together  from  a 
very  short,  scarcely  perceptible  trunk,  and  are  of  nearly  equal  size.  The  bronchial 
supply  of  the  right  Inng  differs  materially  from  that  of  the  left.  About  2  centimetres 
from  the  bifurcation  the  trachea  gives  off  a  small  bronchus,  which  supplies  the  right 
cephalic  lobe  exclusively.  At  the  bifurcation  the  right  bronchus  sends  a  short 
branch  to  the  small  median  or  azygos  lobe  and  one  to  the  ventral  lobe. 

The  major  portion  of  the  large  intestine  of  the  pig  consists  of  a  duplicature  which 

1614 2 


18 

is  coiled  upon  itself  somewhat  like  a  watch  spring.  The  caecum  is  bound  down  to 
the  dorsal  wall  of  the  abdominal  cavity  on  the  right  side.  Similarly  the  rectum  and 
a  small  portion  of  adjacent  colon  is  fastened  down  by  peritoneal  folds.  If,  starting 
from  ciecum  and  rectum  as  fixed  points,  the  entire  large  intestine  be  folded  on  itself 
at  the  middle  point  of  its  length  and  the  whole  coiled  up,  beginning  at  this  point  as 
the  free  central  end,  we  have  imitated  the  general  arrangement  of  the  large  intestine 
in  the  abdomen.  The  coiled  part  is  loosely  bound  together  and  readily  movable  in 
the  abdomen.  As  regards  the  dimensions  the  following  measurements  are  taken  from 
a  male  pig  about  7  months  old,  and  39  inches  long  from  the  tip  of  snout  to  root  of  tail. 
The  intestine  was  distented  with  normal  feces  :  1,  csecurn,  extending  from  closed  end 
to  ileo-caecal  valve,  7£  inches  long ;  2,  from  valve  to  duplicature  or  bend  in  the  center 
of  the  coil,  5  feet ;  3,  from  the  latter  point  to  anus,  6  feet.  It  will  be  noticed  that  the 
folding  takes  place  in  the  middle  of  the  entire  length  of  the  largo  intestine. 

In  the  description  of  the  regions  the  duplicature  is  a  convenient  point  at  which  to 
distinguish  the  upper  from  the  lowercolon.  Where  the  rectum  begins  it  would  be  diffi- 
cult to  determine  without  careful  anatomical  observations.  Provisionally,  its  limit 
if  determined  by  its  old  original  signification  may  be  placed  at  eight  to  twelve  inches 
from  the  external  opening  or  anus. 

In  examining  the  large  intestine  it  is  best  to  begin  the  separation  at  the  fold  or 
bend  in  the  center  of  the  coil  and  continue  until  the  ca'cum  and  lower  colon  are 
reached.  The  caecum  is  easily  removed  with  the  small  intestine  attached.  The  lower 
colon  is  associated  with  the  duodenum  in  the  same  mesentery  and  is  crossed  by  it. 
Care  must  be  taken  not  to  injure  either  tube  at  this  point  in  attempting  to  separate 
them.  In  beginning  it  is  best  to  tie  a  string  around  the  tube  at  the  flexure  as  a 
landmark  for  future  reference. 

The  writer  has  used,  apparently  without  discrimination,  the  English 
and  the  metric  system  of  weights  and  measures.  It  will  be  noticed, 
however,  that  in  the  more  strictly  scientific  part  of  the  work  only  the 
metric  system  is  used,  while  in  those  portions  which  may  be  interesting 
to  a  wider  circle  the  English  system  is  substituted. 


BRIEF  SUMMARY  OF  EARLIER  INVESTIGATIONS— 1886-' 88. 


During  the  summer  of  1886  the  writer  made  a  number  of  post-mortem 
examinations  of  diseased  pigs  iu  Illinois,!  for  the  purpose  of  identifying, 
if  possible,  the  swine  diseases  existing  in  the  Western  States  with  the 
disease  of  hog  cholera  (or  swine  plague  as  it  was  then  denominated), 
under  observation  since  November,  1885,  on  the  Experiment  Station 
near  Washington.  It  will  be  remembered  that  the  hog-cholera  bacillus 
was  discovered  in  November  of  1885,  and  carefully  studied  as  to  its 
morphological  and  pathogenic  characters. 

The  post-mortem  examinations  were  made  in  the  field,  the  spleen 
removed,  placed  in  a  sterilized  bottle,  and  the  cultures  made  either  im- 
mediately or  several  hours  later,  indoors.  During  the  first  visit  to 
Illinois  iu  July,  1886,  pigs  were  examined  in  Marion,  Champaign,  and 
Henry  Counties.  In  some  cases  the  lungs  were  diseased.  In  most  cases 
the  intestines  were  more  or  less  ecchymosed,  while  ulcers  or  indurations 
of  the  mucous  membrane  were  rare.  What  was  most  surprising,  how- 
ever, was  the  absence  of  any  bacteria  in  the  spleen  of  seven  out  of 
eight  animals  examined.  In  the  eighth  case  there  was  considerable 
pneumonia  associated  with  pigmentation  of  the  mucosa  in  the  large 
intestines.  The  culture  from  the  spleen  contained  two  species  of  bac- 
teria, the  bacillus  coll  communis,  a  common  inhabitant  of  the  digestive 
tract  of  the  pig  and  other  domesticated  animals,  and  a  small,  non-motile 
bacterium  which  possessed  pathogenic  properties  as  the  inoculations 
made  at  that  time  distinctly  demonstrated.  These  bacteria  were  isolated 
by  inoculating  a  rabbit  subcutaneously  with  a  bouillon  culture  contain- 
ing both  kinds  of  bacteria.  The  rabbit  died  in  7  days  with  exten- 
sive inflammation  of  the  subcutaneous  tissue  starting  from  the  point  of 
inoculation.  Cultures  from  the  spleen,  liver,  and  blood  contained  only 
one  form,  the  oval  non-motile  bacterium.  A  second  rabbit,  which  re- 
ceived one-sixth  cubic  centimetre  of  a  pure  bouillon  culture  of  these 
bacteria  under  the  skin,  died  in  3  days  with  beginning  peritonitis.  Two 
mice,  inoculated  in  the  same  manner,  died  respectively  1  and  2  days  after 
inoculation. 

'Already  published  in  detail  in  various  reports  of  the  Department  of  Agriculture. 
tSee  Report  of  the  Bureau  of  Animal  Industry  for  1886,  p.  76. 

19 


20 

• 

Much  time  was  spent  in  studying  the  motile  bacillus,  owing  to  its 
superficial  resemblance  to  hog-cholera  bacilli.  Any  one  familiar  with 
intestinal  bacteria  will,  I  think,  at  once  concede,  after  reading  the  de- 
scription on  page  78  of  the  report  referred  to,  that  this  was  the  bacillus 
coli.  The  peculiar  expanding  and  rapid  growth  on  gelatine,  the  coagu- 
lation of  milk,  the  offensive,  putrescent  odor  of  the  cultures,  are  prop- 
erties which  do  not  belong  to  hog  cholera  bacilli.  Moreover  there  was 
no  manifestation  of  any  pathogenic  power.  The  small  non-motile 
bacteria  were  identical  with  those  named  throughout  this  report  as 
swine-plague  bacteria. 

H. 

Several  months  later  the  writer,  having  found  the  information  ob- 
tained on  this  journey  quite  different  from  what  was  expected,  under- 
took another  journey  in  the  same  State.*  As  usual  the  various  re- 
ports of  swine  disease  found  in  the  papers  vanished  before  the  writer's 
approach,  and  after  much  search  a  herd  was  found  near  Sodorus, 
Champaign  County,  in  which  a  number  of  animals  had  already  perished 
and  some  were  very  sick.  Two  of  the  latter  were  killed.  In  No.  1 
there  were  extensive  pneumonia  and  some  large  ulcers  in  the  large  in- 
testine. In  No.  2  there  were  the  same  pneumonia,  a  very  large  spleen, 
and  one  ulcer  on  the  valve  in  the  large  intestine.  Various  cultures 
were  made  at  the  time  and  blood  was  collected  in  pipettes  which  were 
sealed  in  the  flame.  The  result  of  the  bacteriological  examination  was 
briefly  as  follows : 

From  No.  1 :  The  spleen  contained  only  hog-cholera  bacteria.  The 
blood  (first  pipette)  hog-cholera  bacteria  and  streptococci.  The  blood 
(second  pipette)  contained  only  swine-plague  bacteria. 

From  No.  2:  The  spleen,  blood,  and  pleural  cavity  each  contained 
swine-plague  bacteria. 

Sections  of  the  lung  tissue  of  No.  2,  hardened  in  alcohol,  showed  large 
numbers  of  swine-plague  bacteria  in  the  alveoli. 

With  swine-plague  bacteria  from  the  pleural  tube  cultures  of  pig  No. 
2  a  considerable  number  of  inoculations  were  made  upon  smaller  ani- 
mals to  determine  their  pathogenic  power  as  compared  with  the  swine- 
plague  bacteria  already  found.  The  inoculations  were  made  by  inject- 
ing definite  quantities  of  bouillon  cultures  which  had  been  inoculated 
from  single  colonies  on  gelatine  plates. 

One  mouse,  one-eighth  cubic  centimetre  subcutaneously,  dies  in  48  hours. 
One  mouse,  three-sixteenths  cubic  centimetre  subcutaneously,  dies  in  24  hoars. 
One  mouse,  one-twelfth  cubic  centimetre  subcutaneously,  dies  in  2  days. 
One  mouse,  one-twelfth  cubic  centimetre  subcutaneously,  dies  in  6  days. 

In  these  animals  there  were  no  marked  lesions.  In  some  the  bacteria 
injected  were  present  in  large  numbers  in  the  various  organs ;  in  others 
they  were  very  scarce. 

*L.  c.,  p.  79. 


21 


One  rabbit,  one-eighth  cubic  centimetre  subcutaneously,  dies  in  4  daya. 
One  rabbit,  one-fourth  cubic  centimetre  subcutaneously,  dies  in  5  days. 
One  rabbit,  one-eighth  cubic  centimetre  subcutaneously,  dies  in  3  days. 

In  the  rabbits  at  the  place  of  inoculation  the  subcutis  was  much 
thickened  by  purulent  infiltration,  and  there  was  more  or  less  hemor- 
rhagic  and  exudative  peritonitis.  In  the  exudate  the  injected  bacteria 
were  very  abundant. 

One  pigeon,  one-half  cubic  centimetre  subcutaneously,  dies  in  2  days. 
One  pigeon,  three-fourths  cubic  centimetre  subcutaneously,  dies  in  4  days. 

At  the  place  of  the  inoculation  the  muscular  tissue  more  or  less 
necrosed.  Bacteria  not  detected  in  the  internal  organs. 

One  guinea-pig,  one-fourths  cubic  centimetre  subcutaneonsly,  dies  in  6  days  with 
slight  local  changes  and  exudative  peritonitis  and  pleuritis. 

One  fowl,  one-half  cubic  centimetre  subcutaneously,  dies  in  5  days. 

One  fowl,  1  cubic  centimetre  subcutaneously,  recovered. 

In  both  there  was  extensive  necrosis  of  the  pectoral  muscle  at  the  place  of  inocu- 
lation. 

The  following  animals  were  inoculated  by  rubbing  into  the  subcu- 
taneous tissue  through  an  incision  a  loop  dipped  into  a  gelatine  cul- 
ture: 

One  guinea-pig  (abdomen)  dies  in  5  days;  subcutaneous  lesion  very  extensive. 

One  guinea-pig  (abdomen)  dies  in  8  days;  subcutaneous  lesion  very  extensive. 

One  mouse  (root  of  tail)  dies  in  3  days. 

One  mouse  (root  of  tail)  dies  in  4  days. 

One  rabbit  (ear)  dies  in  9  days ;  extensive  subcutaneous  lesions. 

Two  pigeons  (breast)  remain  well. 

One  fowl  (breast)  remains  well. 

From  cultures  of  the  swine-plague  bacteria  derived  from  the  blood 
of  pig  No.  1  two  rabbits  were  inoculated  to  see  if  the  bacteria  from 
both  cases  were  identical. 

One  rabbit  received  one  twenty-fourth  cubic  centimetre  bouillon  culture;  died  in 
3  days. 

One  rabbit  received  a  loop  of  gelatine  culture ;  died  in  10  days. 
In  both  there  was  much  local  inflammation  in  the  subcutis  and  peritonitis. 

With  cultures  of  the  swine-plague  bacteria  from  these  two  sources  a 
number  of  pigs  were  inoculated  as  indicated  in  the  table  : 


Pigs. 

Date  of  in- 

ocnlation. 

Quantity 
injected. 

Source  of  culture. 

Remarks. 

No  287 

Sept  11  1886 

c.  c. 
*2} 

Genesco.  Ill    ........ 

No  289 

do    

*2£ 

....do  

No  363 

Oct.  30  1886 

*5 

do  

No.  367 

..do  

ti 

do  

No  effect 

No.  330 

Oct.     4,  1886 

*5 

Sodorus,  111    

No  331 

do 

*3 

.  .  .  do  . 

No.  364 

Oct.   30,  1886 

*5 

do  

Dies  in  8  days  •  jaundice. 

No.  366 

do  

ti 

....do  

No  effect. 

No.  374 
No.  375 

Nov.  18,  1886 
do  

*5* 
*5 

....do  
....do  

Dies  in  11  days  ;  jaundice. 
Dies  in  7  days;  jaundice. 

*  Subcutaneous. 


t  Into  right  lung. 


22 

It  will  be  seen  that  of  these  ten  pigs  eight  were  inoculated  subcu- 
taneously  with  doses  ranging  from  2£  to  5  cubic  centimetres  of  a  bouil- 
lon culture.    Two  died  from  I  to  2  mouths  after  inoculation,  the  remain- 
ing six  in  from  7  to  18  days  thereafter  with  a  peculiar  disease  of  the  r 
liver  and  generalized  jaundice. 

Two  inoculated  into  the  lung  tissue  through  the  right  chest  wall  re- 
mained unaffected. 

The  liver  in  these  cases  was  greatly  enlarged  and  so  firm  that  when 
removed  from  the  body  there  was  no  change  of  form.  There  was  no 
obstruction  to  the  flow  of  bile  in  the  bile  ducts.  The  disease  of  the 
liver  tissue  itself  was  shown  in  sections  of  cases  289  and  375  to  be  due 
to  inflammatory  foci  within  the  lobules.  In  some  of  these  foci  the  pa- 
renchyma cells  were  still  visible,  but  very  feebly  stained  ;  the  trabecular 
arrangement  was  destroyed  j  the  nuclei  of  the  cells  very  much  shriveled 
or  absent.  In  other  foci  the  parenchyma  was  replaced  by  numerous 
round  cells.  From  these  observations  it  would  seem  that  the  disease 
consisted  of  necrosis  of  a  mass  of  hepatic  cells  followed  by  round  cell 
infiltration.  These  foci  varied  in  size  from  one-eighth  to  one-half  the 
area  of  the  lobule.  Almost  every  lobule  was  affected,  either  several 
small  areas  or  one  large  area  of  disease  being  present  in  each,  situated 
usually  near  the  periphery.  In  No.  375  there  was  also  very  extensive 
cellular  infiltration  beneath  the  capsule.* 

That  the  disease  was  induced  by  the  inoculation  can  not  be  very  well 
denied  in  view  of  the  facts  in  the  case.  The  animals  used  were  from 
four  different  lots  purchased  from  four  different  owners.t  No  other 
animal  in  these  lots  died  with  these  lesions  of  the  liver.  The  inocula- 
tions must,  therefore,  be  considered  as  the  direct  cause  of  the  fatal 
result. 

These  experiments  are  in  so  far  remarkable  as  future  subcutaneous 
inoculations  with  swine-plague  bacteria  from  other  sources,  with  one 
exception,  produced  no  effect.  1  have  not  observed  this  disease  since 
the  time  these  experiments  were  made.  The  only  explanation  which 
can  be  made  is  that  these  varieties  of  swine-plague  bacteria  had  a 
slightly  different  pathogenic  power  which  manifested  itself  in  the  man- 
ner described. 

*  Much  ill'Considered  criticism  has  been  leveled  at  these  experiments  and  results 
hy  F.  S.  Billings,  and  they  are,  therefore,  presented  again  simply  to  show  the  un- 
founded character  of  these  criticisms.  While  the  term  cirrhosis  used  in  the  earlier 
reports  may  not  have  exactly  expressed  the  diseased  condition  of  the  liver,  it  should 
also  he  remembered  that  the  field  of  comparative  pathology  is  not  sufficiently  devel- 
oped to  aid  us  in  choosing  terms  or  in  finding  certain  diseases  already  described  and 
named. 

tNos.  287-294,  bought  June  1,  1886,  when  8  weeks  old,  from  Mr.  M. ;  Nos.  329-335, 
bought  Aug.  27,  1886,  when  8  weeks  old.  from  Mr.  B. ;  Nos.  363-367,  bought  Oct.  18, 
1886,  when  8  weeks  old,  from  Mr.  J. ;  Nos.  368-382,  bought  Oct.  18,  1886,  when  8 
weeks  old,  from  Mr.  J.  F. 


23 


III. 

Toward  the  close  of  1886*  Dr.  Paaren  sent  to  the  Bureau  portions  of 
lungs  from  Cerro  Gordo  County,  Iowa.  These  portions  indicated  con- 
solidation of  the  lung  tissue  with  necrotic  foci  and  exudative  pleuritis. 
By  inoculation  into  mice  and  rabbits  swine-plague  bacteria  were  ob- 
tained, which,  reinoculated  in  pure  culture,  produced  death  within  24 
hours.  The  bacteria,  very  abundant  in  the  internal  organs,  showed 
distinctly  the  polar  stain.t  They  did  not  differ  in  any  respect  from  the 
bacteria  found  in  Illinois,  excepting  in  their  greater  virulence  on  the 
smaller  experimental  animals.  Two  pigs  inoculated  subcutaneously 
with  5  cubic  centimetres  each  did  not  manifest  any  signs  of  disease. 

IV. 

In  February  of  1887  an  outbreak  of  swine  disease  came  under  obser- 
vation which  showed  conclusively  the  transmissibility  of  the  lung  dis- 
ease and  the  bacteria  which  are  the  cause. 

The  disease  was  associated  in  every  case  with  pneumonia  and  pleuritis 
of  a  more  or  less  severe  character.  In  the  course  of  the  disease  casea- 
tion  of  the  involved  lung  tissue  was  frequently  observed.  Intestinal 
lesions  of  a  kind  hitherto  observed  but  once  beforef  were  present  in  the 
earlier  cases.  These  investigations  have  been  criticised  by  F.  S.  Bil- 
lings, if  his  statements  deserve  the  name  of  criticism,  because,  in  addi- 
tion to  the  swine-plague  bacteria  found  iu  almost  every  case,  hog-cholera 
bacilli  were  detected  in  the  later  cases.  It  is  difficult  to  discover  from 
his  statements  which  of  the  two  bacteria  he  objects  to.  His  own  report 
leaves  us  wholly  in  the  dark  which  kind  he  himself  has  found  in  Ne- 
braska, owing  to  the  ambiguous  manner  in  which  the  bacteria  found  by 
him  have  been  described.  We  may  therefore  pass  over  these  criticisms 
and  briefly  summarize  the  investigations§  which  have  since  been  con- 
tinned  by  much  more  extended  ones. 

On  January  31  a  small  number  of  pigs  were  purchased  from  a  farm 
adjoining  the  Experiment  Station  for  the  purpose  of  testing  the  effect 
of  different  cathartics  on  the  healthy  pig.  The  animals  had  been  pur- 
chased from  this  farm  because  no  disease  had  existed  there  for  several 
years.  These  pigs  (Nos.  40ii-406,  inclusive)  were  put  in  a  pen  by  them- 
selves. On  the  following  day  one  (No.  406)  was  found  dead  with  exten- 
sive ulceratiou  of  the  large  intestine,  but  no  lung  disease.  This  occur- 
rence of  course  spoiled  the  entire  experiment  as  planned.  The  disease 
was  regarded  as  hog  cholera  by  me,  although  I  did  not  examine  the 

*L.c.,p.92. 

t  For  the  meaning  of  this  expression,  sec  p.  85. 
t  Report  of  the  Bureau  for  1886,  p.  Cti. 

$  For  a  full  account  of  the  autopsy  notes  and  bacteriological  examination,  see  report 
of  the  Bureau  for  1887,  p.  86. 


24 

aiiimal  or  make  cultures,  being  engaged  in  other  work  at  the  time.  An- 
other fact  which  led  to  the  supposition  that  this  disease  was  different 
from  the  disease  which  appeared  later  in  the  other  animals  of  this  lot 
was  told  by  the  owner.  Nos.  405  and  406  were  the  only  pigs  which  had 
not  been  confined  in  pens,  and  which,  therefore,  may  have  been  ex- 
posed to  infection  on  the  farm  which  did  not  reach  the  penned  animals. 
At  the  time  No.  406  died  (February  1),  the  other  animals  appeared 
well.  Some  of  these  were  distributed  into  small  pens  by  themselves 
and  fed  different  doses  of  cathartics.  Meanwhile  no  other  animal  of 
this  lot  died  until  15  days  later,  when  403  died.  The  following  table 
gives  information  concerning  the  rest : 


Pigs. 

Date  of 
death. 

Kemarks. 

No.  400 

Feb.l... 

Intestinal  ulcers. 

No.  403 

No.  405 
No.  402 

Feb.  16... 
Feb.  18... 
Feb.  19... 

Ventral  lobes  of  lungs  diseased  ;  cvoupous  inflammation  of  large  intestine. 
Extensive  pneumonia  and  pleurilis  ;  croupous  inflammation  of  large  intestine. 
Slight  pneumonia  ;  croupous  inflammation  of  large  intestine. 

No.  404 

Not  affected. 

As  regards  the  bacteriological  examination  the  following  may  be  said : 

No.  406.  None  made  because  disease  supposed  to  be  hog  cholera. 
No.  403.  None  made  for  same  reason. 

No.  405.  Swine-plague  bacteria  found  in  lungs ;   other  organs  not  examined. 
No.  402.  Bouillon  cultures  made  from    pleural  shreds,  spleen,  liver,  and  blood. 
Gelatine  cultures  made  from  blood  and  liver. 

Nearly  all  the  cultures  from  No.  402  contained  a  large  spore-bearing 
bacillus  which  I  have  frequently  found  since  then  in  cases  of  swine  dis- 
ease having  hemorrhagio  lesions.  Cultures  from  the  liver  and  blood 
contained  also  swine-plague  bacteria  which  were  isolated  by  rabbit 
inoculation. 

It  will  be  noticed  that  in  the  later  cases,  Nos.  403,  405,  and  402,  the 
large  intestine  was  the  seat  of  a  peculiarly  intense  inflammation,  ac- 
companied by  the  exudation  of  circumscribed  masses  of  fibrin  easily 
lifted  away  from  the  mucosa,  leaving  a  paler,  slightly  depressed  spot 
showing  no  necrosis  of  tissue.  In  the  rectum  this  exudate  formed  a 
continuous  sheet  also  easily  removable. 

It  might  be  claimed  that  the  feeding  of  a  dose  of  aloes  or  salts  may 
have  caused  this  peculiar  intestinal  inflammation.  This  claim,  however, 
is  effectually  disposed  of  by  case  No.  407.  This  animal,  one  of  the  same 
herd,  had  not  been  taken  from  the  neighboring  farm.  It  was  found 
dead  February  22,  and  brought  to  the  Station  for  examination.  The 
notes  of  this  case  are  reproduced  because  it  must  be  considered  the 
most  trustworthy  of  all. 

No.  407.  Pig  of  medium  size,  white  ;  skin  of  abdomen,  chest,  neck,  and  back  deeply 
reddened.  Fat  abundant,  slightly  reddened  along  the  linea  alba.  Superficial 
inguinal  glands  slightly  enlarged ;  spleen  dotted  with  elevated  blood- red  points.* 

*  These  points  are  found  in  spleens  of  healthy  swine. 


25 

Stomach  and  duodenum  normal,  the  latter  bile-stained.  In  ileum  Peyer's  patches 
are  visible  as  groups  of  small,  dark  dots  ;  no  swelling.  Mucosa  of  ctBCiim  and  upper 
colon  of  a  dirty  blackish  color,  probably  pigmented.  A  few  haomatomata  beneath 
mucosa.  Besides  the  diffuse  pigmentation  the  niucosa  is  sprinkled  with. isolated  or 
confluent  masses,  about  one-eighth  to  one-fourth  inch  in  diameter,  of  a  dirty  grayish- 
yellow  color,  loosely  adherent  to  the  membrane.  When  pulled  away  a  slightly 
depressed  surface  is  exposed.  Much  of  this  mass  can  be  easily  removed  by  simply 
moving  the  scalpel  over  it.  There  are  several  ulcers  in  the  caecum  with  decided  loss 
of  substance.  The  patch  of  mucous  glands  at  the  base  of  the  valve  is  also  converted 
into  an  ulcerated  mass.  Lymphatic  glands  in  abdomen  slightly  swollen  and  red- 
dened. Kidneys  deeply  reddened  to  tips  of  papillae. 

On  opening  the  thorax  the  lungs  did  not  collapse,  and  a  rather  disagreeable  odor 
was  perceived.  As  in  No.  405,  the  ventral  and  cephalic  lobes  of  both  lungs  were 
consolidated.  The  hepatized  regions  were  very  hard  to  the  touch,  bright  red,  with 
yellowish  points  sprinkled  in  regularly.  (See  Plates  in  and  iv.)  The  right  lung 
was  adherent  to  chest  wall  over  the  hepatized  portion.  A  whitish,  spongy  mem- 
brane was  interposed,  about  one-eighth  to  one-fourth  inch  thick,  inclosing  a  small 
quantity  of  turbid  liquid.  On  removing  the  lungs  the  membrane  remained  adherent 
to  the  pulmonary  pleura,  and  was  removed  with  difficulty.  A  portion  of  the  dia- 
phragm was  also  firmly  attached.  The  left  lung  adhered  firmly  to  the  chest  wall  in 
two  places,  where  it  was  consolidated.  The  costal  pleura  was  deeply  reddened, 
owing  to  the  injection  of  a  close  net-work  of  minute  vessels.  Trachea  and  bronchi 
filled  with  whitish  foam. 

On  section,  the  consolidated  region  is  sharply  but  irregularly  marked  off  from  the 
normal  tissue,  very  consistent  and  slightly  elevated.  The  color  varies  from  a  bright 
red  to  a  grayish  red.  In  all,  minute  grayish  points  are  present  one-twelfth  inch  in 
diameter,  about  the  same  distance  apart,  and  of  a  hazy  outline.  The  smaller  bronchi 
are  filled  with  a  purulent  fluid.  In  the  surrounding  lobules  in  which  the  disease  is 
more  advanced  the  interlobular  tissue  is  distended  with  a  serous  infiltration ;  the 
large  vessels  are  filled  with  very  consistent  dark  clots.  Heart  rather  large,  pericar- 
dium free ;  right  auricle,  ventricle,  and  large  veins  distended  with  clots ;  small 
white  clot  in  left  ventricle. 

Microscopic  examination  of  the  lung  tissue  in  cover-glass  preparations  shows  the 
presence  of  numerous  bacteria  with  the  polar  stain  in  recent  lesions  ;  in  older  ones 
they  are  rare.  Other  forms  are  present,  but  only  in  small  numbers.  The  pleural 
exudate  was  made  up  of  rounds  cells,  bound  together  by  bundles  of  fibrin ;  it  con- 
tains few  bacteria. 

In  transverse  sections  of  the  large  intestine,  where  a  mass  of  exudate  is  still 
attached,  the  muscular  and  submucous  layers  are  intact,  if  we  except  a  slight  cellu- 
lar infiltration  near  the  base  of  the  crypts.  The  mucous  layer,  however,  is  consider- 
ably changed.  The  surface  epithelium,  including  a  portion  of  the  crypts  of  Lieber- 
kiihn,  is  no  longer  distinguishable,  but  merges  without  demarcation  into  an  exudate 
several  millimetres  thick,  consisting  of  leucocytes  imbedded  in  a  mesh-work  of  fibrin, 
the  whole  refusing  to  stain. 

Pure  cultures  of  swine-plague  bacteria  in  tubes  of  gelatine  were  obtained  from  the 
plenral  exudato.  In  each  needle  track  a  large  number  of  colonies  developed.  A 
piece  of  false  membrane  gave  the  same  result.  Cover-glass  preparations  from  spleen 
and  liver  were  negative.  Two  tubes  of  beef  infusion  into  which  bits  of  spleen  had 
been  dropped  remained  sterile.  Two  similar  cultures  from  the  liver  contained  each 
a  large  bacillus,  evidently  of  post-mortem  growth.  The  blood  from  the  heart  was 
also  free  from  bacteria,  for  two  tubes  of  gelatine,  each  inoculated  six  or  seven  times 
with  blood,  did  not  develop  a  single  colony. 

A  rabbit  inoculated  in  the  ear  with  a  bit  of  lung  tissue  died  within  4  days.  There 
was  no  swelling  or  reddening  of  the  ear.  Lungs  deeply  congested  (hypostaticf). 
Immense  numbers  of  awine-plague  bacteria  in  blood,  spleen,  and  liver.  Cultures 


26 

from  blood  and  liver  contained  the  same  organisms.  A  mouse  inoculated  with  a 
bit  of  lung  tissue  succumbed  within  2  days.  Bacteria  very  scarce  in  body.  Pure 
cultures  of  swiue-plagiie  bacteria  were,  however,  obtained  from  heart's  blood. 

What  is  of  importance  in  this  case  and  in  No.  402  is  the  absence  of 
hog-cholera  bacilli  from  the  internal  organs  where  we  would  certainly 
expect  to  find  them  in  this  disease.  If  we  refuse  to  consider  the  intes- 
tinal lesions  as  caused  by  swine-plague  bacteria,  we  have  the  alter- 
native of  assuming  the  existence  of  bacteria  which  produce  intestinal 
disease  without  penetrating  into  the  internal  organs  proper.* 

Five  other  cases  in  this  investigation  deserve  special  attention.  Nos. 
408,  409,  and  410  of  the  same  herd  still  remained  on  the  farm.  .After 
the  examination  of  407  had  s\hown  the  absence  of  hog  cholera,  and  the 
presence  in  the  diseased  lungs  of  swine-plague  germs,  and  the  evidence 
thus  far  obtained  pointed  to  a  different  disease  caused  by  the  latter 
bacteria,  two  pigs,  Nos.  359  and  360,  were  taken  from  the  Station  to  the 
farm  and  penned  with  the  three  mentioned  to  determine  whether  the 
disease  is  readily  communicable.  This  was  done  February  28.  March 
5,  No.  408  died.  March  16  the  remaining  four  were  taken  back  to  the 
Station  and  placed  in  aii  unused  pen  free  from  infection,  so  as  to  be 
under  observation. 

Of  these  four  pigs  No.  409  died  March  20,  No.  410,  March  29.  Of  the 
exposed  animals  No.  359  died  March  24,  24  days  after  the  commence- 
ment of  the  exposure ;  No.  360,  April  6,  37  days  thereafter.  Of  these 
four  cases  No.  360  was  not  examined.  Of  the  remaining  three,  hog- 
cholera  bacilli  were  detected  in  409  by  rabbit  inoculation,  but  not  in 
either  408  or  410,  while  swine-plague  bacteria  were  found  in  408  and 
359.  Looking  over  the  original  notes  I  am  convinced  that  the  number 
of  cultures  made  from  the  spleens  of  408, 410,  and  359  were  sufficient  to 
enable  us  to  exclude  the  presence  of  hog  cholera  from  these  cases.  No. 
409  is  therefore  the  only  animal  from  the  adjoining  farm  which  was  ex- 
amined in  which  hog-cholera  bacilli  were  detected.  It  is  likewise 
strange  that  in  the  spleen  of  No.  408  a  bacillus  should  appear  resem- 
bling hog-cholera  bacillus  in  many  respects,  but  not  identical  with  it, 
and  producing  only  suppuration  in  rabbits. 

The  cases  which  came  under  observation  subsequently,  and  in  which 
hog-cholera  bacilli  were  readily  demonstrated  in  the  spleen,  were  Station 
pigs  which  had  been  exposed  some  time  ago  to  the  infection  of  hog 
cholera.  These  cases  are  chiefly  valuable  in  pointing  out  that  the  swine- 
plague  bacteria  are  transmitted  from  animal  to  animal  and  associated 
with  lung  disease.  They  may  be  thrown  out  altogether,  since  the 
source  of  the  hog-cholera  bacilli  is  traceable. 

No.  372.  Fed  viscera  of  hog  cholera  case  December  24, 1886,  iu  infected 
pen. 

*  By  "  internal  organs  "  I  mean  those  organs  which  do  not  come  in  contact  with  the 
air  or  food,  either  directly  or  indirectly.  Thus  the  entire  respiratory  and  digestive 
tract  may  be  regarded  as  external,  so  far  as  bacteria  are  concerned. 


27 

No.  378.  Fed  viscera  of  hog  cholera  case  November  18,  1886,  in  in- 
fected pen.  Fi'd  viscera  of  406  February  2,  in  infected  pen. 

No.  392.  Inoculated  with  swine  plague  bacteria  (Iowa)  January  25; 
placed  in  the  infected  pen  March  28. 

No.  397.  Fed  viscera  of  378  in  pen  7  March  24. 

In  372,  392,  397,  both  hog  cholera  and  swine  plague  bacteria  were 
found.  Their  presence  in  the  old  infected  pen  or  their  contact  with 
pigs  kept  there  will  account  for  this  double  infection. 

The  facts  brought  out  by  this  investigation  corroborated  those  al- 
ready brought  out  in  the  investigations  of  the  preceding  year.  They 
showed  the  existence  of  pneumonia  and  pleuritis,  together  with  intesti- 
nal disease  in  most  of  the  animals  examined,  associated  with  bacteria 
readily  distinguished  from  hog-cholera  bacteria. 

They  also  demonstrated  the  transmissibility  of  the  pneumonia  to  other 
pigs,  and  in  these  pigs  the  same  bacteria  were  found. 

If  the  lesions  of  the  large  intestine,  as  observed  in  the  early  cases, 
were  due  to  hog-cholera  bacilli,  why  were  these  bacilli  not  found  ex- 
cepting in  one  late  case  in  which  there  may  have  been  an  accidental 
infection  of  the  rabbit  inoculated  f  Why  were  hog-cholera  bacilli  read- 
ily detected  in  the  later  cases  kept  in  the  infected  pen  ? 

While  these  investigations  do  not  prove  that  the  swine-plague  bac- 
teria were  the  cause  of  the  intestinal  lesions,  they  also  do  not  seem  to 
show  any  relationship  between  these  lesions  and  hog-cholera  bacilli. 
This  question  of  the  relation  between  intestinal  lesions  and  swine- 
plague  bacteria  will  be  discussed  farther  on.* 

V. 

In  September,  1888,  an  outbreak  of  swine  disease  near  Baltimore, 
Md.,  came  to  our  notice.  Three  pigs  from  one  herd  and  one  from  another 
herd  were  examined.  The  following  synopsis  of  the  cases  may  be  of 
interest,  the  full  account  being  given  elsewhere. t 

Pig  No.  1.  Broncho-pneumonia;  exudate  on  mucosa  of  rectum  and 
lower  colon ;  swine-plague  bacteria  detected  in  lungs  and  rectum  ;  hog- 
cholera  bacilli  in  spleen. 

Pig  No.  2 :  Three-quarters  of  both  lungs  hepatized ;  ulcers  in  ileum 
and  colon;  swine-plague  bacteria  in  lungs;  hog-cholera  bacteria  in 
spleen. 

Pig  No.  3 :  Extensive  pneumonia  and  pleurisy ;  ulceration  of  large 
intestine;  swine-plague  bacteria  in  lungs;  hog  cholera  bacteria  in  spleen. 

Pig  No.  4:  Slight  atelectasis  of  lungs;  ulcers  in  large  intestine; 
s  wine-plague  bacteria  in  large  intestine;  hog-cholera  bacteria  in  spleen. 

Pig  No.  3  was  taken  to  the  Experiment  Station,  where  it  became  the 
starting  point  of  a  mixed  outbreak  of  hog  cholera  and  pneumonia. 

*  P.  102. 

t  Report  of  the  Bureau,  etc.,  l887-'88,  p.  121. 


28 

VI. 

During  November,  1888,  the  writer  was  directed  to  make  some  in- 
vestigations in  Iowa,*  where  swine  diseases  at  that  time  were  prevail- 
ing to  a  considerable  extent.  In  the  vicinity  of  Mason  City  pigs  from 
three  herds,  some  distance  apart,  were  examined.  The  lesions  observed 
were  both  intestinal  and  pulmonary.  The  intestinal  lesions,  though 
varying  considerably  in  appearance  and  intensity,  did  not  differ,  on  the 
whole,  from  those  observed  in  hog  cholera.  The  lung  lesions  varied 
considerably  in  character  and  extent,  from  a  slight  collapse  in  a  single 
lobe  to  almost  total  hepatization,  accompanied  by  exudative  pleuritis. 

The  investigations  were  limited  to  post-mortem  examination  and 
cultures  from  the  spleen.  From  each  spleen  small  bits  of  tissue  were 
removed  to  two  tubes  of  agar.  In  addition,  portions  of  diseased  lung 
tissue  and  ulcerated  mucous  membrane  from  the  large  intestine  were  cut 
out  and  transferred  to  sterile  test  tubes  plugged  with  cotton  wool  for 
inoculation  into  rabbits.  Ten  pigs  were  examined  in  this  manner. 

In  but  one  case  did  the  spleen  pulp  show  any  bacteria  under  the 
microscope,  and  in  this  case  they  were  streptococci.  En  but  one  agar 
tube  of  the  spleen  series  did  anything  develop.  This  was  a  motile 
bacillus,  resembling  the  hog-cholera  bacillus  in  form,  but  differing  in 
its  growth  on  agar,  in  bouillon,  and  in  gelatine,  this  growth  being  in 
all  cases  more  vigorous.  Of  two  mice  and  one  rabbit  inoculated,  one 
mouse  died  in  5  days.  The  lesions  were  indefinite  and  did  not  point 
to  hog  cholera.  Moreover,  the  other  mouse  and  the  rabbit  remained 
unaffected. 

With  particles  of  diseased  lung  tissue  and  mucous  membrane  from 
some  of  these  cases  a  considerable  number  of  rabbits  and  some  mice 
were  inoculated.  Of  those  that  died  some  contained  no  bacteria  of  any 
description.  Those  inoculated  from  three  cases  out  of  ten  died  of 
swine  plague  since  these  bacteria  were  found.  A  few  survived  the 
inoculation. 

The  nature  of  this  disease  was  not,  therefore,  cleared  up  by  these  in- 
vestigations, since  the  results  were  not  uniform.  While  in  hog  chol- 
era the  bacilli  are  present  in  the  spleen,  and  readily  obtained  therefrom 
by  cultivation,  they  were  not  present  in  the  spleens  of  these  ten  cases. 
As  already  stated,  swine-plague  bacteria  were  obtained  from  three  cases. 
They  were  quite  virulent,  as  the  inoculations  upon  pigs  show.  Thus 
one  pig,  which  received  9  cubic  centimetres  of  a  bouillon  culture  into 
the  right  lung  .through  the  chest  wall,  died  within  20  hours  of  septi- 
caemia, the  injected  bacteria  being  present  in  the  spleen  in  considerable 
numbers.  Another  pig,  which  received  a  subcutaneous  injection  at  the 
same  time,  remained  well.  Somewhat  later  two  pigs  received  into  the 
right  lung  1J  cubic  centimetres  and  3  cubic  centimetres  of  a  bouillon 

'Report  of  the  Bureau  of  Animal  Industry  for  1887-'88,  pp.  135-145,  where  a  de- 
tailed account  of  this  work  is  given. 


29 

culture.  The  one  which  had  received  the  smaller  dose  was  sick  for  a 
time,  but  recovered.  It  was  killed  1  £  months  after  the  inoculation,  and 
both  lungs  were  found  everywhere  adherent  to  the  chest  wall.  In  the 
pericardial  sac  a  considerable  quantity  of  pus  had  collected,  in  which 
the  injected  bacteria  were  still  present,  as  determined  by  cultures. 

The  animal  which  had  received  the  larger  dose  became  very  ill  and 
was  killed  5  days  after  inoculation.  At  the  autopsy  were  detected  par- 
tial hepatization  of  the  right  lung,  with  extensive  exudative  pleuritis 
and  pericarditis. 

The  two  following  cases,  which  have  not  yet  been  published,  demon- 
strate very  strikingly  the  virulence  of  these  bacteria.  The  growth  on 
a  number  of  agar  cultures  about  9  days  old  was  scraped  off  and  trans- 
ferred to  sterile  bouillon  until  a  turbid  suspension  was  obtained.  This 
suspension  was  prepared  because  these  bacteria  multiply  very  feebly 
in  bouillon,  and  when  the  latter  is  used  as  the  injecting  fluid  very  few 
bacteria  are  actually  introduced  into  the  body.  This  turbid  suspension 
was  used  to  inoculate  2  pigs.  No.  120  received  into  the  abdomen  2 
cubic  centimetres;  No.  143  into  the  right  lung  through  the  chest  wall 
but  1  cubic  centimetre.  The  inoculation  was  made  March  11, 1889, 
over  3  mouths  after  the  bacteria  had  been  obtained  from  the  diseased 
swine. 

No.  120.  Essex  female,  5  months  old.  Into  the  right  lung  through  the  chest  wall, 
2  cubic  centimetres  of  above  suspension  injected  with  hypodermic  syringe,  6  p.  m. 
March  11.  Found  dead  early  next  morning. 

Subcutaneous  inguinal  glands  partly  hemorrhagic.  From  the  cut  subcutaneous 
vessels  of  right  side  liquid  blood  oozes  out.  In  abdomen  the"  solitary  follicles  of 
large  intestine  appear  as  bright  red  circular  spots  three-sixteenths  inch  diameter,  as 
seen  from  serosa.  Spleen  slightly  engorged. 

Large  quantity  of  blood-stained  serum  in  right  pleura!  sac.  The  needle  had  punc- 
tured the  convex  surface  of  principal  lobe,  where  there  was  some  infiltration  of  blood. 
A  thin  layer  of  fibrin  on  convex  surface  of  the  small  anterior  lobes  and  on  pericardium. 
A  few  collapsed  lobules  along  free  border  of  these  lobes. 

In  stomach,  the  mucosa  of  fundus  is  deeply  reddened  over  an  area  of  3  to  4  square 
inches;  in  this  area  two  hemorrhagic  spots.  The  upper  half  of  duodenum  with 
mucosa  intensely  reddened.  Contents  somewhat  blood-stained.  All  Peyer's  patches 
iff  the  small  intestine  from  duodenum  to  ileo-csecal  valve  are  intensely  reddened, 
the  follicles  appearing  as  blood-red  points.  On  some  patches,  hemorrhages  on  the 
surface.  Considerable  number  of  ascarides  in  small  intestine.  In  large  intestine 
the  lymphatic  patch  near  valve  likewise  reddened.  Mesenteric  and  mesocolic  glands 
hyperaemic. 

Kidneys  very  much  congested.  The  glomeruli  appear  as  minute  blood-red  points. 
Small  quantity  of  nrine  in  bladder  loaded  with  albumen.  Blood  fails  to  clot.  In 
the  spleen  large  numbers  of  swine  plague  bacteria. 

No.  143.  Essex  male,  5  months  old.  Injected  into  abdomen  1  cubic  centimetre  of 
turbid  suspension  of  swine  plague  bacteria,  March  18.  Animal  dies  40  hours  after 
inoculation. 

Inguinal  glands  slightly  swollen  and  hyperiemic.  In  abdominal  cavity  peritoneum 
pale  pink,  all  minute  vessels  injected.  Shreds  of  a  viscid  grayish  exudate  attached 
to  abdominal  walls,  contiguous  coils  of  intestines,  and  stomach.  Considerable  opaque 
reddish  serum  present.  Vessels  of  diaphragm  injected;  some  ecchymoses  observed. 
The  shreddy  exudate  also  present.  The  mesentery  oadematons,  especially  where 


30 

attached  to  intestines.  The  walls  of  a  portion  of  the  lower  small  intestine  very 
much  swollen,  serosa  dark  red.  On  the  mucosa  which  is  congested  a  yellowish, 
pasty  exudate  loosely  rests,  occupying  the  side  to  which  mesentery  is  attached. 
This  exudate  is  made  up  of  leucocytes  imbedded  in  strands  of  fibrin.  Peyer's  patches 
along  this  region  and  down  to  ileo-csecal  valve  are  deeply  congested  and  swollen  so 
as  to  appear  boat-shaped.  (The  bacteria  had  evidently  traveled  along  mesentery 
and  invaded  the  walls  of  the  small  intestine.) 

Large  intestine  distended  with  dry  feces.  Mucosa  of  caecum  and  colon  more  or 
less  congested,  the  congestion  limited  mainly  to  summits  of  folds.  The  lymphatic 
patch  near  valve  very  hypersemic  and  swollen. 

In  each  pleural  sac  about  50  cubic  centimetres  of  reddish  serum.  A  thin  membra- 
nous exudate  covering  the  dependent  half  of  both  lungs  easily  scraped  away  as  a 
pale  yellowish  pnlpy  mass.  The  remainder  of  pleura  opaque,  a  barely  visible  exu- 
date covering  it.  The  lungs  are  hypersemic,  the  free  border  of  the  ventral  and  ce- 
phalic lobes  collapsed.  Bronchial  glands  swollen  and  hypenemic. 

Pericardium  thickened,  clouded  ;  vessels  injected.  A  barely  visible  exudate  on  it. 
Vessels  of  heart  surface  very  much  distended.  Petechi;»  on  left  auricle  and  under 
endocardium  of  left  ventricle  near  semi-lunar  valves.  Eight  heart  distended  with  a 
dark,  soft  coagulum. 

In  the  peritoneal  exudate,  which  consists  chiefly  of  fibrin  and  a  few  leucocytes, 
immense  numbers  of  the  injected  bacteria  are  present,  showing  after  staining  the 
polar  arrangement  of  protoplasm  very  distinctly.  The  pleural  exudate  composed  of 
the  same  elements.  In  some  leucocytes  up  to  twenty  bacteria.  In  the  spleen  and 
blood  from  the  heart  large  numbers  of  swine-plague  bacteria.  Agar  cultures  from 
the  spleen,  pleural,  and  peritoneal  cavities  contain  only  the  injected  bacteria.  A 
bouillon  culture  from  the  spleen  likewise  pure. 


INVESTIGATIONS  OF  1889-'90. 


The  problem  of  swine  diseases  as  it  stood  after  the  completion  of 
these  investigations  up  to  1889  may  be  stated  briefly  as  follows: 

Since  1885  a  well-characterized  bacillus  has  been  encountered  as  the 
cause  of  an  infectious  disease  termed  hog  cholera,  which  is  chiefly 
localized  in  the  large  intestine.  Since  1886  our  attention  has  been 
directed  to  lung  disease  in  swine  with  which  a  bacterium  is  associated, 
which,  when  inoculated  into  swine,  proves  to  be  very  virulentand  may  give 
rise  to  pneumonia  when  the  bacteria  are  injected  into  the  lungs.  This 
is  sufficient  to  demonstrate  the  existence  of  a  disease  differing  from  hog 
cholera,  which  has  been  called  swine  plague  because  an  identical  dis- 
ease of  swine  in  Germany,  first  described  in  1885,  was  called  Schweine- 
seuche.  This  lung  disease  was  shown  to  be  communicable.  (IV.)  * 

In  many  of  the  outbreaks  examined  the  changes  found  in  the  intes- 
tines could  not  be  distinguished  from  hog  cholera  (except  perhaps  in 
IV).  In  some  hog-cholera  bacilli  were  actually  detected,  in  others 
(I,  VI)  they  could  not  be  found.  One  of  the  problems,  therefore,  still 
before  us,  and  a  very  important  one,  was  to  determine  whether  all  out- 
breaks of  swine  plague  in  which  intestinal  lesions  closely  resembling 
those  of  hog  cholera  are  present  are  mixed  outbreaks  of  swine  plague 
and  hog  cholera,  or  are  simply  swine  plague. 

Much  light  has  been  thrown  upon  this  subject  by  the  investigations  of 
three  outbreaks  given  in  detail  in  the  following  pages.  The  first  is  a 
mixed  outbreak  in  which,  however,  the  lung  lesions  are  so  very  well 
marked  and  the  swine-plague  bacteria  associated  with  these  lesions  so 
virulent  that  there  can  be  little  doubt  that  the  hog  cholera  disease  was 
really  secondary  to  the  swine  plague.  The  second  outbreak  is  simple, 
uncomplicated  swine  plague.  In  the  third  outbreak  very  virulent  swine- 
plague  bacteria,  and,  in  one  case,  very  attenuated  hog-cholera  bacilli 
were  found. 

VII. 

An  outbreak  of  swine  disease  appeared  among  the  pigs  belonging  to 
an  abattoir  adjoining  the  Experiment  Station  about  the  first  week  in 
October,  1889.  The  disease  came  to  our  notice  a  week  after  the  first 


These  numerals  refer  to  the  different  outbreaks  as  numbered,  in  this  report. 

31 


32 

animals  died,  and  in  attempting  to  trace  the  causes  which  led  to  it  we 
obtained  the  following  information : 

The  pigs  were  purchased  in  the  markets  of  Washington  City  the  lat- 
ter part  of  September.  They  were  thirty-five  in  number,  in  two,  possi- 
bly three,  lots.  One  lot  came  in  two  crates.  It  could  not  be  deter- 
mined whether  it  was  made  up  of  pigs  from  one  or  two  sources.  They 
began  to  die,  as  stated,  about  a  week  after  their  arrival.  We  examined 
in  all  thirteen  animalSj  the  first  on  October  12,  the  last  on  October  28. 
A  few  days  later  the  last  of  these  thirty-five  pigs  succumbed  to  the  dis- 
ease. It  lasted,  therefore,  about  1  month.  A  few  large  swine  which 
were  on  the  place  when  these  animals  arrived  did  not  take  the  infection. 

In  the  following  pages  a  detailed  statement  of  the  pathological  and 
the  bacteriological  examination  is  given.  Those  who  are  not  specially 
interested  in  these  notes  will  find  a  summary  of  the  ascertained  facts 
following  them. 

No.  1.  October  12.  Male  pig,  weighing  about  25  pounds,  died  last  night.  On  inner 
aspect  of  right  thigh  an  area,  about  one-half  inch  in  diameter,  of  extravasation,  ex- 
tending down  into  true  skin.  No  ulcers  in  the  mouth.  Spleen  not  enlarged. 

Contents  of  stomach  slight  in  amount,  consisting  chiefly  of  sand  and  a  turbid 
liquid ;  walls  contracted,  throwing  mucosa  into  large  folds.  The  greater  part  of 
mucosa  intensely  congested.  In  the  fundus  a  large  ulcer  1£  inches  across,  covered  by 
a  slough  one-quarter  inch  thick.  The  subjacent  wall  nearly  one-half  inch  thick,  on 
section  deeply  reddened  throughout,  due  to  a  sanguinolent,  oedematous  infiltration 
of  the  wall.  Adjacent  to  this  a  smaller  inflammatory  thickening  covered  with  a  thin 
pultaceous  slough.  The  mucosa  of  duodenum  uniformly  and  deeply  pigmented.  In 
the  ileum  the  mucosa  is  swollen,  Foyer's  patches  reddened. 

Mucosa  of  caecum  of  a  bluish-gray  color,  dotted  with  a  small  number  of  ulcers  not 
much  larger  than  pins'  heads,  covered  with  yellowish  sloughs.  Similar  follicular 
ulcers  on  Foyer's  patch  near  valve.  Upper  colon  contains  much  earth,  adhering  rather 
closely  to  mucosa.  The  latter  quite  deeply  pigmented,  the  pigmentation  intensified 
in  lower  colon.  In  upper  colon  a  small  number  of  flattish  yellowish-white  sloughs 
from  one-sixteenth  to  one-eighth  inch  in  diameter. 

In  thorax,  the  pleura  covering  the  diaphragm  and  ribs  is  overlaid  by  a  pale 
pinkish  membranous  exudate,  easily  rubbed  off  and  especially  abundant  on  the  right 
side. 

The  various  lobes  of  both  lungs  firmly  glued  together  by  exudate.  The  ventral 
lobes,  the  major  portion  of  cephalic  lobes,  and  a  small  portion  of  the  principal  lobes 
adjacent  to  the  ventrals  are  hepatized.  The  hepatized  areas  are  covered  by  false 
membranes  varying  in  thickness  and  easily  peeled  off.  Through  the  hepatized  lobes 
are  disseminated  necrotic  masses  of  a  greenish  color  varying  in  size  from  mere  specks 
to  peas.  They  contain  large  numbers  of  swine-plague  bacteria,  which  show  a  polar 
stain  very  clearly.  The  tissue  around  the  terminal  portion  of  both  bronchi  in  the 
principal  lobes  is  hepatized  and  contains  necrotic  foci.  Lung  worms  abundant  in 
the  left  bronchus.  Both  bronchi  contain  small  quantities  of  reddish  foam.  Peri- 
cardium thickened,  opaque ;  vessels  injected ;  iho>  ventral  surface  is  covered  by  a 
membranous  exudate  and  it  is  adherent  to  the  heart  surface  by  means  of  a  similar 
exudate.  Cover-glass  preparations  from  the  pleural  and  pericardial  exudate,  from 
various  regions  of  hepatized  lung  tissue,  contain  large  numbers  of  swine-plague  bac- 
teria. 

A  rabbit  was  inoculated  October  12,  by  placing  a  bit  of  lung  tissue  under  the  skin 
of  abdomen.  Dead  next  morning.  Slight  ecchymosis  in  the  subcutis  at  the  point 
of  inoculation.  The  blood  and  spleen  contain  immense  numbers  of  swine-plague 


33 

bacteria,  showing  well  the  polar  arrangement  of  the  protoplasm  when  stained.  Cul- 
tures confirmatory,  agar  and  bouillon  being  used  chiefly. 

A  rabbit  inoculated  at  the  same  time  and  in  the  same  way  with  a  bit  of  spleen 
tissue.  Rabbit  dead  next  morning.  Swine-plagne  bacteria  fewer  than  in  preceding 
case.  An  agar  culture  from  the  blood  contains  only  these  germs.  From  the  spleen  two 
agar,  one  bouillon,  and  one  gelatine  tube  culture  prepared.  On  the  second  day  (Sun- 
day intervening)  a  moderate  number  of  isolated  colonies  on  the  agar  surfaces ;  the 
condensation  water  turbid  with  flaky  deposits.  In  the  bouillon  tube  are  a  large 
number  of  minute  suspended  flakes,  the  liquid  itself  not  clouded.  In  these  cultures 
only  swine-plague  bacteria.  The  gelatine  tube  remained  sterile. 

From  the  pleural  exudate  an  agar  and  a  bouillon  tube  were  inoculated  at  the 
autopsy.  On  the  second  day  a  number  of  colonies  similar  to  those  on  the  spleen  agar 
culture  were  found  to  be  made  up  of  swine-plague  bacteria.  The  bouillon  culture 
faintly  and  uniformly  clouded.  Only  swine-plague  germs  present.  From  the  epicar- 
dial  exudate  two  similar  cultures  were  prepared  with  the  same  result,  with  the  ex- 
ception that  in  the  bouillon  culture  large  cocci  were  also  present. 

With  a  bit  of  lung  tissue  taken  from  more  recently  diseased  regions  two  gelatine 
rolls  and  two  agar  plates  were  made.  In  the  second  gelatine  roll  about  100  minute 
colonies  present  after  3  or  4  days.  These  were  examined  and  bouillon  tubes  inocu- 
lated from  four  different  colonies  at  different  times.  In  all  the  swine-plague  germs 
only  appeared.  The  first  agar  plate  developed  a  very  large  number  of  colonies,  the 
second  only  six  or  seven,  made  up  only  of  swine-plague  germs. 

No.  2.  Female;  died  last  night;  weighs  about  35  pounds.  Lymphatics  in  the  groin 
barely  enlarged,  pale.  Spleen  quite  large,  softened,  dark  red  in  color. 

Digestive  tract :  Stomach  partly  filled  with  chewed  leaves,  and  straw  adhering 
slightly  to  mucosa.  Fundus  faintly  reddened.  The  pyloric  portion  bile-stained. 
Duodenum  similarly  stained.  An  ascaris  in  the  bile  duct,  projecting  1|  inches  out 
into  duodenum.  Arborescent  injection  of  mucosa  of  the  latter.  Considerable  quan- 
tity of  turbid  liquid  in  large  bowels.  Mucosa  not  pigmented.  Peyer's  patch  at  base 
of  valve  thickened  and  pigmented.  Ulcers  moderately  abundant  in  csecum  and 
upper  colon.  They  appear  as  little  cup-shaped  depressions,  one-sixteenth  to  one- 
eighth  inch  iu  diameter, lined  with  a  pale  yellowish  uecrotic  layer,  the  center  in  some 
filled  with  a  black  slough  and  the  margin  elevated.  Mesenteric,  mesocolic  glands, 
and  those  of  lesser  omentuin,  slightly  swollen  ;  cortical  layer  congested.  Interlobu- 
lar  markings  of  liver  prominent,  broadened.  The  section  appears  mottled,  some  lob- 
ules being  much  more  congested  than  others.  The  empty  gall-bladder  contains  a 
partly  disintegrated  ascaris,  which  extends  through  bile  duct  into  duodenum. 

Thorax:  The  costal  pleura  of  both  sides  highly  injected  and  covered  with  a  thin, 
whitish  membranous  exudate,  gluing  the  lungs  to  the  chest  wall.  Of  the  lungs  all 
but  a  small  strip  along  the  dorsal  border  of  the  principal  lobes  is  solid,  three  or  four 
times  the  size  of  the  normal  lung  when  collapsed.  The  various  lobes  are  glued  to 
each  other,  forming  a  single  mass,  in  which  the  individual  lobes  are  not  recognizable, 
and  which  is  in  turn  attached  to  the  chest  wall,  the  diaphragm,  and  the  pericardium 
by  pleuritic  exudate.  This  is  most  abundant,  and  forms  membranes  on  the  most  de- 
pendent portions  of  the  lungs,  easily  pulled  away  from  the  subjacent  structures.  The 
various  adhesions  torn  without  difficulty. 

The  disease  seems  farthest  advanced  in  the  cephalic  and  ventral  lobes,  in  which 
are  imbedded  a  large  number  of  closely  set  masses  of  dead  tissue,  from  one-sixteenth 
to  one-half  inch  in  diameter.  These  are  firm,  yellowish  masses,  sharply  defined  in 
outline,  and  imbedded  in  dark  red  hopatized  tissue,  which  is  mottled  with  paler 
specks,  representing  the  ultimate  lobules  distended  with  cell  masses. 

The  trachea  and  bronchi  contaiu  whitish  foam,  mixed  with  large  quantities  of 
thick,  purulent  secretion.  In  the  bronchi  of  the  principal  lobes  are  many  lung 
worms.  The  bronchial  glands  are  hypenernic  and  cedeniatons,  and  contain  a  small 
number  of  necrotic  foci. 

1614- — 3 


34 

In  lihe  spleen  a  few  minute  oval  bacteria  detected.  With  a  platinum  needle  the 
surface  of  an  agar  tube  and  a  bouillon  tube  inoculated.  On  following  day  the 
former  showed  a  considerable  number  of  round,  grayish  colonies,  1|  to  3  millimetres 
(one-sixteenth  to  one-eighth  inch)  in  diameter;  condensation  water  clouded.  In  this 
tube  only  swine-plague  germs  detected.  The  bouillon  culture  contains  a  considerable 
number  of  minute  granules,  representing  clumps  of  swine-plague  bacteria. 

An  agar  culture  from  the  liver  grew  like  the  spleen  culture  and  contained  only  swine- 
plague  germs. 

At  the  autopsy  an  agar  and  a  bouillon  tube  inoculated  from  the  right  pleura.  In 
the  former  only  the  condensation  water  became  turbid  and  contains  swine-plague 
germs  exclusively.  The  bouillon  tube  remains  sterile ;  similarly  a  bouillon  tube  from 
pericardial  exudate  remains  sterile.  (It  is  highly  probable  that  the  flocculent  growth 
of  the  swine-plague  germs  in  bouillon  and  the  sterility  of  these  tubes  was  occasioned 
by  an  unsuitable  condition  of  the  bouillon.) 

From  a  bit  of  lung  tissue,  the  pleural  surface  of  which  had  been  thoroughly 
scorched,  gelatine  roll  cultures  were  prepared.  After  a  number  of  days  the  first  roll 
showed  a  large  number  of  colonies  as  mere  points,  the  second  roll  about  100  colonies, 
somewhat  larger.  From  both  tubes  bouillon  was  inoculated  from  individual  colonies. 
These  contained  after  development  only  swine-plague  bacteria. 

At  the  same  time  the  scorched  lung  tissue  was  pricked  with  platinum  needle  and 
an  agar  tube  inoculated.  On  the  surface  a  considerable  number  of  similar  colonies 
appeared  on  the  following  day.  Some  of  these  examined  were  swine-plague  germs. 
In  the  condensation  water  a  few  chains  of  a  short,  motionless  rod  appeared  among 
the  great  bulk  of  swine-plague  germs. 

At  the  same  time  a  rabbit  was  inoculated  from  the  lung  tissue.  It  was  dead  next 
morning.  Enormous  numbers  of  polar  stained  swine-plague  germs  found  in  stained 
preparation  of  spleen  pulp.  An  agar  culture  confirms  the  microscopic  examination. 

No.  3.  Died  last  night.  Female ;  weighs  about  25  pounds ;  in  very  poor  condition. 
Spleen  considerably  engorged;  contains  a  small  number  of  bacteria;  nature  to  be 
determined  by  cultivation. 

Digestive  tract :  One  ulcer  on  the  gums  of  lower  jaw.  Stomach  contents  like 
those  of  No.  2.  In  the  fundus  an  area  of  mucosa,  about  4  inches  in  diameter,  is  nearly 
black  from  extravasation,  and  thickened.  A  zone  several  inches  wide  outside  of  this 
is  deeply  reddened.  The  mucosa  of  duodenum  and  ileuin  more  or  less  discolored  the 
vessels,  showing  arborescent  injection.  In  the  caecum,  the  mucosa  is  of  a  bluish- 
gray  color,  and  dotted  with  a  dozen  sloughs,  one-eighth  inch  diameter,  of  a  yellow 
color;  the  tissue  at  the  margin  of  the  slough  thickened,  elevated.  The  Peyer's  patch 
near  valve  deeply  congested  and  sprinkled  with  enlarged  grayish  follicles.  Mucosa 
of  colon  more  or  less  discolored  and  hypersemic  in  patches  ;  only  three  small  ulcers 
found.  The  liver  appears  normal,  the  bile  in  bladder  very  thick,  flaky.  Punctiform 
ecchymoses  on  surface  of  kidneys. 

In  the  lungs  the  major  portion  of  both  ventral  lobes  is  solidified,  the  tips  being 
emphysematous.  The  hepatized  portions  are  bright  red  in  color,  with  faint  yellow- 
ish mottling. 

Bacteriological  examination  :  Cover-glass  preparations  of  the  hepatized  lung  tissue 
show  no  bacteria.  From  a  bit  of  tissue  two  gelatine  roll  cultures  prepared  and  a 
rabbit  inoculated.  Roll  A  subsequently  contained  a  large  number  of  apparently  iden- 
tical colonies.  Roll  B,  about  fifty  of  the  same  colonies  and  one  chromogene.  Care- 
ful examination  of  these  revealed  hog-cholera  bacilli.  The  inoculated  rabbit  died 
within  36  hours.  At  the  place  of  inoculation  the  bit  of  lung  tissue  was  surrounded 
by  a  small  area  of  purulent  infiltration  and  dilated  blood-vessels.  In  the  blood  and 
spleen  a  very  large  number  of  swine-plague  bacteria.  A  bouillon  culture  from  the 
blood  faintly  clouded  on  the  following  day,  and  holding  in  suspension  barely  visible 
granules  made  up  of  clumps  of  swine-plague  bacteria.  No  motile  bacteria  detected. 

The  spleen  of  the  pig  contained  a  few  bacteria,  character  not  determinate.     With  a 


35 

bit  of  pulp  a  gelatine  roll  A  and  agar  plate  B  prepared,  also  a  bouillon  culture.  The 
latter  was  uniformly  clouded  on  the  following  day  ;  a  few  gas  bubbles  on  the  surface. 
Only  motile  hog-cholera  bacteria  present.  The  presence  of  hog-cholera  bacilli  in  the 
spleen  was  furthermore  demonstrated  by  the  roll  and  plate  culture.  The  agar  plate 
grew,  of  course,  most  rapidly,  being  in  the  thermostat.  On  the  second  day  a  consid- 
erable number  of  colonies  appeared,  apparently  the  same.  Examination  of  some 
showed  only  hog-cholera  bacilli.  A.  bouillon  tube  inoculated  from  one  of  them  was 
clouded  on  the  following  day  with  motile  hog-cholera  bacilli. 

One-fifth  cubic  centimetre  of  the  original  bouillon  culture  was  injected  subcuta- 
neously  into  a  rabbit.  On  the  fourth  day  temperature  106.1°  F.  Found  dead  on  the 
seventh  day  with  the  usual  lesions  of  hog  cholera,  such  as  engorged  spleen,  necrotic 
foci  in  the  liver,  reddened  Peyer's  patches,  hemorrhagic  points  on  the  lower  colon 
and  rectum.  Spleen  and  liver  contain  hoy-cholera  bacilli  in  moderate  numbers. 
From  spleen  an  agar  and  a  bouillon  culture  prepared  by  piercing  spleen  with  a  fine 
platinum  needle  and  inoculating  culture  media  therewith.  In  both  only  hog-cholera 
bacilli  appeared.  The  original  spleen  culture  contained  no  swine-plague  germs, 
otherwise  the  rabbit  would  have  succumbed  within  1  or  2  days. 

In  the  gelatine  roll  appeared  after  a  few  days  a  very  large  number  of  the  same 
colonies,  evidently  all  hog  cholera. 

No.  4.  October  14.     Small  male  pig,  weighing  about  30  pounds  ;  died  last  night. 

Skin  of  abdomen  slightly  reddened.  Subcutaneous  inguinal  glands  enlarged, 
cedematous,  mottled  red  and  pale. 

Mouth  free  from  ulcers.  Contents  of  stomach  stained  with  bile.  Mucosa  of  fundus 
over  an  area  4  inches  square  deeply  congested,  swollen.  Slight  injection  of  minute 
vessels  in  duodenum;  remainder  of  small  intestine  normal.  Large  intestine  con- 
tains a  turbid  liquid  and  a  substance  resembling  coal  ashes.  The  mucosa  of  caecum 
studded  with  superficial,  yellowish  sloughs,  about  the  size  of  pins'  heads  or  a  little 
larger.  In  the  colon,  besides  these  small  yellowish  sloughs  there  are  three  or  four 
large  areas  over  which  the  mucous  membrane  is  entirely  necrosed  superficially. 
These  areas  are  about  6  inches  long.  The  minute  sloughs  limited  chiefly  to  the 
upper  half  of  the  colon. 

Liver  rather  firm  in  texture,  the  acini  projecting  slightly  above  iuterlobular  tissue 
on  the  surface.  Glands  near  the  portal  fissure  deeply  congested  throughout. 

Dilatation  of  pelvis  of  kidneys  encroaching  on  medullary  portion  to  a  large  extent. 
Both  ureters  very  much  distended;  walls  from  one-half  to  three-quarters  inch  thick. 

Lungs  collapse  when  removed  from  thorax;  no  pleuritis.  In  all  the  lobes  there 
are  masses  of  collapsed  and  hepatized  tissue  varying  in  diameter  from  one-half  to 
several  inches.  They  are  situated  chiefly  near  the  roots  of  the  lobes.  The  small 
median  lobe  in  part  hepatized,  bright  red  with  yellowish  mottling.  In  the  terminal 
bronchi  are  plugs  of  lung  worms  imbedded  in  thick  muco-pus.  The  tissue  around 
the  plugs  in  the  loft  principal  lobe  hepatized. 

Bacteriological  examination:  With  bits  of  diseased  lung  tissue  two  gelatine  rolls 
were  prepared  and  a  rabbit  inoculated.  The  rolls  both  contained  on  the  second  day 
an  immense  number  of  colonies  of  micrococci,  evidently  a  contamination  of  the  gela- 
tine. The  inoculated  rabbit  died  in  4  diiys  with  enlarged  spleen  and  patches  of 
necrosis  in  the  liver  in  the  form  of  a  net  work.  An  agar  culture  from  the  spleen  and 
a  bouillon  culture  from  heart's  blood  both  subsequently  contained  only  hog-cholera 
bacilli.  No  swine-plague  germs  detected,  although  the  rather  premature  death  of 
the  rabbit  led  mo  to  suspect  their  presence.  Some  weeks  later  a  rabbit  was  inocu- 
lated subcutaneously  in  the  ear  with  a  platinum  loop  of  the  blood  culture  of  the 
preceding  rabbit.  This  rabbit  died  in  5  days  with  hog-cholera  lesions. 

With  a  bit  of  spleen  pulp  of  the  pig  a  gelatine  roll  A  and  an  agar  plate  B  were 
prepared;  also  a  bouillon  tube  inoculated  with  platinum  neeille  after  pricking  the 
spleen.  This  developed  into  a  pure  culture  of  hog-cholera  bacilli.  In  the  gelatine 
roll  appeared  numerous  colonies  of  hog-cholera  bacilli.  The  agar  plate  was  partially 
overgrown  ;  the  few  isolated  colonies  were  made  up  of  hog-cholera  bacilli, 


36 

From  the  liver  a  gelatine  roll,  an  agar  and  a  bouillon  tube  inoculated,  each  with 
minute  particles  of  tissue.  In  the  roll  numerous  colonies  appeared,  evidently  all  hog 
cholera.  The  two  tube  cultures  likewise  contained  only  hog-cholera  bacilli. 

No.  5.  October  15.     Small  male  pig,  weighing  about  25  pounds,  died  last  night. 

Skin  about  urinary  meatus  reddened.  Subcutaneous  inguinal  glands  enlarged, 
firm,  juicy,  faintly  mottled  with  red. 

Stomach  contracted.  Contents  same  as  in  preceding  cases.  Mucosa  in  large  folds, 
summits  of  which  somewhat  reddened.  Slight  discoloration  of  mucosa  of  lower  ileum. 
Contents  of  large  intestine  firm,  in  form  of  lumps.  In  the  CSBCUUI  about  ten  ulcers, 
from  one-eighth  to  one-half  inch  in  diameter,  the  largest  button-snapped,  flattish,  a 
firm,  yellowish,  necrotic  base  extending  into  subjacent  muscular  coat.  Complete 
necrosis  of  Peyer's  patch  at  valve.  In  the  colon  a  small  number  of  large  and  small 
button  ulcers.  The  solitary  follicles  projecting  as  large  as  split  peas.  When  squeezed 
a  white  soft  mass  exudes  from  a  central  depression. 

Liver  rather  firm  in  texture.     Gall  bladder  contains  semi-liquid,  flaky  bile. 

Spleen  slightly  enlarged.     Kidneys  on  section  very  pale. 

Both  lungs  O3dematous.  Hepatization  involves  the  free  tip  of  both  small  cephalic 
lobes  of  the  right  lung,  the  major  portion  of  the  ventral  lobe  of  the  left  lung.  In 
both  principal  lobes  are  a  moderate  number  of  small  hepatized  foci.  In  both  bronchi 
a  large  quantity  of  very  viscid  muco  pus,  which  extends  down  into  the  branches  of 
the  principal  lobes.  These  latter  and  the  terminal  portion  of  the  principal  bronchi 
contain  plugs  of  lung  wowus.  Broncbial  glands  enlarged,  firm,  pale. 

Bacteriological  examination:  In  cover-glass  preparations  from  the  spleen  a  very  few 
bacteria  resembling  somewhat  hog-cholera  bacilli  seen.  An  agar  culture  inoculated 
with  platinum  wire  remained  sterile.  On  the  following  day  spleen  taken  from  re- 
frigerator and  a  second  agar  tube  inoculated  with  particle  of  pulp.  In  this  tube  a 
colony  of  greenish  fluorescent  bacilli  appeared. 

From  hepatized  lung  tissue  two  gelatine  rolls  were  prepared.  The  first  one  was 
spoiled  by  a  few  liquefying  colonies;  the  remaining  small  colonies  were  inaccessible. 
The  second  roll  remained  sterile. 

A  rabbit  inoculated  subcutaneously  with  a  particle  of  lung  tissue  died  in  24  hours. 
At  the  place  of  inoculation  considerable  purulent  thickening  of  skin  with  ecchymosis 
of  the  subcutis.  Numerous  very  small  coccidia  cysts  in  liver.  Spleen  enlarged, 
congested.  (Bacteriological  notes  of  this  rabbit  mislaid.) 

No.  6.  October  15.  Small  female  in  very  poor  condition ;  died  last  night ;  more  or 
less  decomposition.  Ventral  aspect  of  body  reddened.  Subcutaneous  inguinal  glands 
enlarged,  firm,  and  very  hyperaemic. 

Stomach  much  contracted,  empty.  Mucosa  of  fundus  beset  with  punctiform  hem- 
orrhages. Small  intestine  not  marked  by  changes  ;  one  ulcer  in  lower  ileum.  Con- 
tents of  caecum  and  colon  of  a  somewhat  pasty  consistency  mixed  with  coarse  sand. 
In  the  caecum  about  six  old,  flattish  ulcers,  from,  one-fourth  to  one-half  inch  in  diam- 
eter, also  a  patch  of  easily  removable,  membranous  exudate  several  inches  square- 
In  the  colon  near  the  valve  several  ulcers  and  a  similar  patch  of  exudate. 

In  the  lungs  the  hepatization,  though  extensive,  is  more  or  less  scattered  in  foci  as 
follows : 

A  few  hepatized  foci  in  left  cephalic,  one  large  hepatized  mass  in  ventral,  and  four 
wedge-shaped  masses  in  left  principal  lobe.  In  the  right  lung,  fully  two-thirds  of  the 
median  and  the  whole  of  the  ventral  lobe  solidified.  The  latter  lightly  glued  to  the 
neighboring  lobes.  Disseminated  through  it  are  very  many  necrotic  foci  about  one- 
eighth  inch  in  diameter.  In  the  right  principal  lobe  several  hepatized  masses.  In 
both  bronchi  a  large  number  of  adult  lung  worms.  Pericardium  thickened ;  vessels 
injected.  Spleen  not  enlarged  or  congested. 

Bacteriological  examination  :  Spleen  found  more  or  less  decomposed.  No  germs  in 
cover-glass  preparation.  In  an  agar  culture  therefrom  numerous  isolated  and  conflu- 
ent hog  cholera  colonies  appeared  on  following  day. 

A  rabbit  inoculated  subcutaneously  with  a  bit  of  lung  tissue  (the  particular  region 


37 

not  indicated  in  the  notes)  was  found  dead  on  tho  eighth  day.  Extending  from  the 
point  of  inoculation  over  the  entire  abdomen  and  portion  of  thorax  the  subcutis  is 
infiltrated  with  a  yellowish,  pasty  mass  of  pus,  stained  with  blood.  The  superficial 
layer  of  muscles  discolored,  ecchymotic.  Spleen  slightly  enlarged.  No  peritonitis. 
Cultures  from  the  spleen  remained  sterile.  An  agar  plate  from  the  subcutaneous  exu- 
date  spoiled  by  condensation  water.  An  agar  tube  from  the  same  source  remained 
sterile. 

No.  7.  October  15.  Small  male  pig,  of  about  35  pounds,  died  yesterday  afternoon 
late  and  put  in  refrigerator  until  next  morning.  Animal  in  fairly  good  condition. 
The  lesions  in  this  case  were  briefly  as  follows: 

Digestive  tract :  Fundus  of  stomach  faintly  reddened.  Small  intestine  not  affected. 
Contents  of  large  intestine  liquid,  of  black  color,  holding  much  earth  in  suspension. 
One  ulcer  on  the  thickened  Peyer's  patch  near  the  valve.  Follicles  swollen.  No  other 
changes. 

Lungs:  General  pleuritis  indicated  on  the  most  dependent  portions  of  the  left  lung 
by  a  thin,  membranous  exudate,  elsewhere  by  roughening.  The  various  lobes  lightly 
glued  together.  Hepatization  limited  to  the  tip  of  the  left  ventral  and  a  small  area 
in  the  left  principal  lobe,  containing  numerous  necrotic  foci.  In  the  right  principal 
lobe  two  wedge-shaped,  hepatized  masses,  in  which  are  many  minute  oval  germs,  re- 
sembling swine  plague.  Generalized  bronchitis  indicated  by  much  curdy  muco-pus 
in  the  bronchi  and  branches.  No  lung  worms  detected. 

In  the  liver,  the  center  of  many  lobules  in  all  the  lobes  of  a  brick-red  color,  caused 
by  fatty  degeneration  of  this  portion  of  the  lobule.  Bile  very  thick,  dark-colored. 

Spleen  very  much  enlarged,  softened,  dark  colored. 

Bacteriological  examination:  From  this  animal  only  the  spleen  and  the  pleural 
exudate  received  any  attention.  An  agar  tube  inoculated  from  the  spleen  simply 
with  a  platinum  wire  was  sterile  on  the  following  day,  although  bacteria  had  been 
detected  in  the  spleen  pulp  in  cover-glass  preparations.  A  second  tube  inoculated 
with  a  particle  of  pulp  from  the  spleen,  kept  meanwhile  in  the  refrigerator,  developed 
a  large  number  of  isolated  and  confluent  colonies.  So  far  as  could  be  determined 
these  were  all  swine-plague  bacteria.  No  motile  bacteria  present. 

An  agar  culture  made  at  the  autopsy  from  the  pleural  exudate  proved  to  be  a  pure 
culture  of  swine-plague  bacteria. 

No.  8.  October  17.  Male  pig,  weighing  about  35  pounds,  died  last  night.  Sub- 
cutaneous inguinal  glands  enlarged,  on  section  dotted  with  minute  petechiie. 

Stomach  normal.  Duodenum  bile-stained.  In  lower  ileum  much  liquid,  containing 
fine  earth  and  sand.  In  ca3cum  minute  vessels  of  mucosa  injected.  Peyer's  patch  at 
valve  somewhat  swollen  and  discolored.  In  the  upper  colon  several  small  patches  of 
thin  exudate,  about  one-fourth  inch  in  diameter ;  the  subjacent  epithelium  appeared 
necrosed.  In  both  kidneys  infarcts  of  a  yellowish,  homogeneous  appearance,  sur- 
rounded by  a  hyperaemic  zone,  and  visible  from  the  surface  of  kidney,  two  in  the  left 
and  twelve  in  the  right. 

Spleen  somewhat  enlarged,  firm.  Liver  very  pale,  pulp  rather  soft.  On  the  left 
lobe  several  paler  spots,  not  elevated,  about  one- fourth  inch  in  diameter.  Bile  thick, 
flaky. 

Lungs  everywhere  adherent  to  surrounding  structures  by  means  of  a  membranous 
exudate,  grayish,  elastic,  coming  away  in  patches  and  shreds  when  pulled.  This 
membrane  especially  thick  between  lungs  and  diaphragm.  The  various  lobes  matted 
together  and  adherent  to  pericardium.  Lungs  do  not  collapse. 

Left  ventral  and  cephalic  lobes  completely  hepatized.  Throughout  both  are  dis- 
seminated a  large  number  of  greenish-white,  homogeneous,  firm  masses  from  one- 
fourth  to  one-half  inch  in  diameter.  Almost  entire  right  lung  hepatized.  In  the 
cephalic  lobe,  ventral  lobe,  and  cephalic  portion  of  principal  lobe  the  necrotic  masses 
are  very  numerous,  one  near  tip  of  ventral  lobe  quite  large.  The  hepatization  of 
the  principal  lobe  is  of  the  dark-red  variety. 


38 

Large  quantities  of  lung  worms  in  left  bronchus  and  branches  contained  in  the 
caudal  third  of  principal  lobe.  Right  bronchus  not  opened.  Pericardium  thickened, 
opaque.  Heart  surface  covered  with  a  thin,  transparent  pseudo-membrane. .  Left 
auricle  hemorrhagic.  A  clot  distending  the  right  heart  and  forming  of  it  a  complete 
cast.  Center  of  clot  pale. 

Bacteriological  examination  :  From  spleen  two  agar  cultures  made.  One  remains 
sterile.  In  the  other  on  second  day  a  faint  growth  starting  from  condensation  water 
upwards.  The  latter  contains  clumps  of  swine-plague  bacteria  and  large  bacilli  with 
terminal  spore.  Several  gas  bubbles  in  agar. 

From  the  pleural  exudate  of  right  lung  an  agar  and  a  bouillon  culture  prepared  at 
autopsy.  On  following  day  a  large  number  of  punctiform  colonies  on  agar  surface. 
Minute  flakes  in  condensation  water.  In  bouillon  minute  granules,  representing 
clumps  of  minute  oval  cocci.  In  both  tubes  only  swine-plague  bacteria. 

From  the  more  recently  hepatized  regions  of  lungs  which  contain  large  numbers  of 
swine-plague  bacteria  and  some  large  bacilli,  two  gelatine  rolls  and  two  agar  plates 
prepared. 

In  the  gelatine  roll  A  two  forms  of  colonies  appeared,  one  with  disk  homogeneous, 
the  other  with  a  distinct  peripheral  zone.  In  roll  B  only  one  kind  appeared.  A 
'  number  of  bouillon  tubes  were  inoculated  from  colonies  in  roll  B  which  turned  out 
to  be  streptococci.  From  roll  A  bits  of  gelatine  were  removed  to  bouillon  with 
warmed  platinum  needle,  some  cultures  remained  sterile  while  others  contained 
streptococci. 

On  the  agar  plate  A,  large  numbers  of  apparently  identical  colonies  appeared.  On 
plate  B,  a  moderate  number  developed.  Of  these  a  few  examined  were  made  up  of 
swine-plague  bacteria. 

A  large  rabbit  inoculated  with  a  particle  of  lung  tissue  died  within  20  hours.  No 
internal  changes,  excepting  a  probably  preexisting  fatty  condition  of  the  liver.  Few 
swine-plague  bacteria  detected  with  the  microscope.  An  agar  and  a  bouillon  culture 
from  heart's  blood  contained  only  swine-plague  bacteria  on  second  day. 

No.  9.  October  18.  Female  pig ;  died  last  night ;  weighs  about  30  pounds.  Sub- 
cutaneous glands  of  groin  enlarged,  firm,  cortex  hyperaemic. 

One  small  necrotic  patch  on  mucous  surface  of  lower  lip.  Stomach  with  fundus 
pale,  pyloric  region  bile-stai  ned.  Around  the  cardiac  expansion  are  about  thirty 
yellowish-white,  confluent,  and  isolated  ulcers  from  one-eighth  to  one-fourth  inch  in 
diameter.  They  are  raised  above  the  level  of  the  mucosa,  flat  on  top.  Projecting 
slough  soft,  friable ;  base  of  nicer  very  firm,  extending  into  muscular  coat.  Mucous 
membrane  of  duodenum  bile  stained ;  arborescent  injection  of  minute  vessels.  Mucosa 
of  ileum  more  or  less  discolored  and  inflamed.  Large  intestine  with  walls  very  much 
infiltrated  aud  mucosa  extensively  destroyed  by  necrotic  changes.  In  the  csecurn,  a 
large  patch  of  ulceration  having  a  peculiar  gnawed  appearance,  surrounding  islands 
of  intact  mucosa.  On  section  the  mucosa  is  found  converted  into  a  yellowish- white, 
firm  mass. 

In  the  colon  patches  like  these  are  interspersed  with  a  large  number  of  isolated  cir- 
cular ulcers  with  blackish,  depressed  surface  and  a  subjacent  yellowish,  firm,  thick 
base  extending  into  the  muscular  coat.  Besides  these,  there  are  a  considerable  num- 
ber of  ulcers  with  an  elevated,  soft,  necrotic  top,  easily  scraped  away.  In  lower  colon, 
large  patches  of  destroyed  mucosa. 

Spleen  very  large,  friable,  pulp  very  dark.  Liver  tissue  apparently  unaffected. 
Bile  rather  thick.  Kidneys  with  parenchymatous  degeneration  of  cortex. 

Lungs  as  whole  much  affected.  In  the  right  lung  all  but  the  dorsal  third  of  the 
ventral  lobe  solid,  enlarged,  bright  red,  with  large  and  small  masses  of  a  pale-greenish 
color  disseminated  through  it.  A  portion  of  the  cephalic  lobe  solid,  in  the  same  con- 
dition. One-half  of  the  median  lobe  similarly  diseased.  The  principal  lobe  glued  to 
ventral  lobe  by  a  thin  pseudo- membrane.  About  one-third  along  the  ventral  aspect 
solidified  in  masses  from  one-half  to  three-fourths  inch  in  diameter,  these  masses  ex- 
tending from  diaphragmatic  to  convex  surface  of  the  lobe.  The  interlobular  tissue 


39 

around  these  hepatized  masses  distended  with  serum.  The  various  lohes  of  the  left 
lung  are  in  the  same  condition  as  the  corresponding  ones  of  the  right  lung.  Pleuritis 
only  over  the  hepatized  regions  in  the  form  of  a  delicate  network. 

The  trachea  and  bronchi  contain  much  frothy  inuco-pus.  In  the  left  terminal 
hronchus,  surrounded  by  hepatized  tissue,  are  masses  of  lung  worms  completely  occlud- 
ing it. 

Bronohial  glands  large,  pale,  containing  a  variable  number  of  amall  necrotic  foci. 

Bacteriological  examination:  From  the  right  pleural  sac  a  bouillon  and  an  agar 
tube  were  inoculated  with  platinum  loop.  In  both  only  swine-plague  bacteria  sub- 
sequently appeared. 

From  a  more  recently  hepatized  region  of  the  lungs  two  agar  plates  were  prepared 
with  a  loop  of  the  serum,  in  which  microscopic  examination  had  shown  an  immense 
number  of  swine-plague  bacteria.  Plate  A  contained,  after  several  days,  a  small  num- 
ber of  miscellaneous  colonies  and  a  very  large  number  of  barejy  visible  colonies,  which 
proved  to  be  made  up  of  swine-plague  bacteria.  On  Plate  B  no  development. 

From  the  more  advanced  disease  two  gelatine  rolls  were  prepared  from  a  particle 
of  necrotic  tissue.  Roll  A  liquefied.  Roll  B,  after  a  week's  time,  contained  about 
twenty-five  small  colonies  of  the  same  character,  resembling  hog  cholera,  and  one  large 
colony.  The  former  transferred  to  agar,  and  bouillon  tubes  proved  to  be  not  hog 
cholera  but  streptococci. 

A  rabbit  inoculated  with  a  bit  of  diseased  lung  tissue  died  within  20  hours.  Organs 
not  changed.  At  point  of  inoculation  considerable  purulent  infiltration.  In  blood 
and  spleen  a  very  large  number  of  swine-plague  bacteria,  showing  in  stained  prepara- 
tions the  polar  stain  very  well.  Cultures  in  bouillon  and  on  agar  confirmatory. 

From  spleen  a  particle  of  pulp  used  to  prepare  one  bouillon  culture  and  an  agar 
plate.  In  the  bouillon  the  motile  hog-cholera  bacilli  appeared  among  clumps  of 
swine-plague  germs.  On  the  plate  after  several  days  a  moderate  number  of  colonies 
of  one  size  and  a  very  large  number  of  colonies  of  a  very  small  size  appeared.  Some 
of  the  former  examined  are  hog-cholera  bacilli,  the  latter  swine-plague  bacteria. 

From  particles  of  liver  tissue  the  same  cultures  were  made,  and  the  same  mixture 
of  hog-cholera  and  swine-plague  bacteria  found. 

Sections  from  more  recent  pneumonic  infiltration  prepared  from  material  hardened 
in  alcohol  show  a  considerable  amount  of  fibrin  in  the  alveoli,  in  whose  meshes  are  a 
few  leucocytes  and  very  many  of  the  minute  swine-plague  bacteria.  The  peribron- 
chial  and  interlobular  lymph  spaces  are  distended  with  fibrin  and  cells  and  contain 
very  many  swine-plague  bacteria. 

Sections  prepared  from  tissue  in  which  the  disease  is  much  more  advanced  show  a 
complete  occlusion  of  the  alveoli  and  small  air  tubes  with  dense  cellular  masses  in 
which  swine-plague  bacteria  are  more  or  less  abundant.  The  tissue  surrounding  such 
foci  contains  in  the  alveoli  a  moderate  number  of  round  cells,  largely  intermixed 
with  fatty  cells.  Bacteria  absent. 

No.  10.  October  19.  Small  male  pig  in  poor  condition,  weighing  21  pounds.  Died 
last  night.  Subcutaneous  inguinal  glands  very  large.  On  section  punctiform  hem- 
orrhages and  irregular  masses  of  apparently  necrosed  tissiie  observed. 

In  the  stomach  a  considerable  number  of  single  and  confluent  ulcers  with  project- 
ing, yellowish,  friable  slough,  resting  on  a  firm,  indurated,  whitish  base.  The  mucosa 
of  small  intestine  shows  extensive  arborescent  injection  of  minute  vessels. 

Contents  of  large  intestine,  a  chocolate-colored  liquid  containing  much  sand. 
The  lesions  of  the  mucous  membrane  are  about  as  extensive  as  in  case  9.  The  larger 
patches  show  more  diptheritic  deposit  than  in  preceding  case. 

Spleen  very  large,  blackish,  friable.     Cystic  degeneration  of  both  kidneys. 

Lungs  extensively  diseased.  Nearly  the  whole  of  the  left  lung  excepting  the  caudal 
half  of  the  principal  lobe  hepatized,  and  covered  with  a  thick  membranous  exudate. 
This  is  readily  peeled  off  in  shreds  and  larger  patches,  especially  dense  on  the  ventral 
and  cephalic  lobe  and  adjacent  pericardium.  Lobes  adherent  to  one  another;  adhe- 


40 

sioiis  easily  loosened.  The  ventral  lobe  is  a  mottled  bright  red.  The  small  air  tubes 
occluded  with  semi-solid  plugs,  easily  squeezed  out.  This  condition  not  observed  in 
the  other  lobes,  excepting  in  the  principal,  in  which  the  terminal  bronchus  and 
branches  are  occluded  with  plugs  of  lung  worms  and  muco-pus. 

In  the  right  lung,  the  ventral  lobe  in  the  same  condition  as  corresponding  lobe  of 
left  side,  containing  in  addition  numerous  necrotic  foci.  The  cephalic  fifth  of  prin- 
cipal lobe  hepatized;  the  hepatization  of  a  bright  red  color,  with  faint  regular  yel- 
lowish mottling.  Cephalic  half  of  the  small  median  lobe  in  the  same  condition. 
The  bronchi  in  the  tip  of  principal  lobe  occluded  with  masses  of  lung  worms  and  in 
part  hepatized.  In  trachea  and  bronchi  much  muco-pus. 

Bacteriological  examination :  In  preparations  from  the  spleen  bacteria  not  detected. 
An  inclined  agar  tube  inoculated  with  platinum  needle  contained  in  a  few  days  a 
large  number  of  minute  apparently  identical  colonies.  So  far  as  could  be  determined 
no  hog-cholera  bacteria  present.  A  bouillon  culture  inoculated  with  a  particle  of 
pulp  contained  both  hog-cholera  and  swine-plague  bacteria. 

From  the  liver  the  same  cultures  prepared.  In  the  agar  tube  besides  a  large  num- 
ber of  small  colonies  are  six  larger  ones.  These  consist  of  hog-cholera  bacilli,  the 
former  of  swine-plague  bacteria.  In  the  bouillon  tube  both  germs  are  present. 

No  inculations  or  cultures  were  made  with  lung  tissue  from  this  case.  An  agar 
and  a  bouillon  tube  were  inoculated  Avith  a  platinum  loop  from  pleural  exudate  at 
the  autopsy.  In  both  only  swine-plague  germs  appeared. 

No.  11.  October  22.  Black  female,  weighing  22|  pounds,  died  last  night.  Subcu- 
taneous inguinal  glands  indurated;  cortex  reddened.  Some  hemorrhagic  points  in 
parenchyma.  Fine  shreds  of  exudate  on  serous  surface  of  large  intestine. 

In  stomach  a  small  quantity  of  food.  Over  the  entire  fundus  the  mucosa  intensely 
congested  and  swollen.  No  ulceration.  Small  intestine  not  affected.  Large  intes- 
tine contains  a  small  quantity  of  turbid  fluid.  Mucosa  much  pigmented.  In  the 
crecum  and  upper  colon  a  small  number  of  ulcers  with  slightly  projecting  slough ; 
lower  colon  considerably  congested.  Follicles  swollen ;  when  compressed,  a  white 
curdy  plug  issues  from  a  central  opening. 

Both -lungs  diseased.  In  the  right  lung  near  the  caudal  border  of  principal  lobe  a 
wedge-shaped  mass  of  hepatized  tissue,  of  a  bright  red  color.  The  peribronchial 
and  interlobular  tissue  infiltrated  over  this  region,  and  the  pleura  covered  with  a 
thin  exudate.  In  the  bronchi  of  this  lobe  are  masses  of  mucus  and  pus  in  which 
lung  worms  are  imbedded.  In  both  cephalic  and  ventral  lobes  are  masses  of  hepa- 
tized tissue;  in  the  former  also  a  large  necrotic  mass. 

The  two  small  lobes  of  the  left  lung  are  converted  into  a  greenish-yellow  n'ecrotic 
mass,  which  cuts  like  firm  cheese.  In  the  principal  lobe  are  three  foci  of  hepatization 
two  of  them,  near  the  tip  of  the  lobe,  where  the  bronchus  and  branches  are  occluded 
with  lung  worms  imbedded  in  mucus. 

Pericardium  thickened,  vessels  injected. 

Cultures  made  in  bouillon  and  on  agar  from  pleural  exudate.  The  bouillon  culture 
contained  after  several  days  only  hog-cholera  bacilli.  The  agar  tube  was  lost.  From 
a  particle  of  lung  tissue  a  gelatine  roll  A,  and  agar  plate  B  prepared.  On  the  agar 
plate  six  small  colonies  appeared,  made  up  of  swine-plague  bacteria.  No  colonies  ap- 
peared in  the  gelatine  roll. 

A  rabbit  was  inoculated  with  a  particle  of  lung  tissue.  It  died  in  9  days  with 
characteristic  hog-cholera  lesions.  Cultures  from  the  spleen  contained  only  hog- 
cholera  bacilli. 

From  the  spleen  and  liver,  bouillon  and  agar  tubes  were  inoculated  with  platinum 
wire.  In  all  four  tubes  only  hog-cholera  bacilli  appeared  subsequently.  . 

No.  12.  October  20.  White  female  pig,  weighing  about  30  pounds.  Died  yesterday 
afternoon  and  placed  in  refrigerator  until  this  morning.  Subcutaneous  inguinal 
glands  enlarged,  hyperarnic.  In  abdominal  cavity  some  dark-colored  serum. 

One  ulcer  on  mucous  surface  of  lower  lip  and  one  on  gums.    Stomach  contracted. 


41 

Considerable  pigmentation  of  mucosa.  Outside  of  cardiac  expansion  two  ulcers  with 
slightly  projecting  slough.  Duodenum  very  deeply  pigmeuted.  Pigmentation  ex- 
tends through  small  intestine.  Similar  dark  pigmentation  of  the  mucosa  of  large  in- 
testine. Foyer's  patch  at  valve  converted  into  numerous  small  yellowish  sloughs 
with  indurated  base.  A  few  specimens  of  trichocephalus  attached  tomucosa.  In 
upper  colon  about  six  small  and  one  larger  nicer  with  indurated  base.  Follicles  much 
enlarged  with  purulent  contents  easily  expressed.  Mesenteric  glands  with  very 
hypenemic  cortex. 

Both  lungs  adherent  to  surrounding  structures.  In  both  pleural  sacs  a  small  quan- 
tity of  clouded  serum.  On  removing  the  lungs  from  thorax,  the  various  lobes  are 
found  bound  together  by  exudate,  the  small  median  lobe  imbedded  in  it  and  the 
diaphragm  adherent  to  base  of  lungs,  the  intervening  exudate  being  very  abundant. 
In  the  right  lung,  both  ventral  and  cephalic  lobes,  hepatized.  On  section  they  have 
a  red,  granular  appearance  mottled  with  grayish  lines  and  patches.  In  the  prin- 
cipal lobe  at  its  caudal  extremity  the  interlobular  tissue  distended  with  reddish 
serum.  Lung  worms  located  here  in  large  numbers.  The  cephalic  portion  of  this 
lobe  where  it  rests  against  the  ventral  lobe  is  hepatized,  bright  red  and  mottled 
with  whitish  points  and  patches,  differing  somewhat  from  the  necrotic  foci  of  former 
descriptions. 

In  the  left  lung  the  ventral  lobe  solid,  resembling  the  corresponding  right  lobe. 
Left  principal  like  the  right.  Lung  worms  in  the  caudal  region. 

Pericardium  thickened,  opaque,  distended  with  yellowish  serum.  The  inner  surface 
lined  with  a  partly  opaque,  partly  gelatinous  exudate.  The  heart  surface  completely 
covered  with  a  thick,  spongy  pseudo-membrane.  (See  plate  x.) 

Spleen  very  slightly  enlarged  and  congested.  Slight  post-mortem  changes  indi- 
cated in  the  appearance  of  the  liver. 

Bacteriological  examination:  In  cover-glass  preparations  from  different  parts  of 
the  lung  tissue  very  many  swine-plague  bacteria  detected.  Two  agar  plates  and  two 
gelatine  rolls  were  prepared.  The  latter  were  spoiled.  On  the  second  agar  plate  a 
large  number  of  minute  colonies  of  the  same  appearance  and  three  or  four  miscella- 
neous colonies.  The  small  ones  are  swine-plague  bacteria. 

A  rabbit  inoculated  with  a  particle  of  lung  tissue  died  within  20  hours.  In  the 
spleen  and  blood  very  many  swine-plague  germs.  In  a  bouillon  culture  the  peculiar 
growth  in  minute  granules  observed  which  this  germ  has  frequently  exhibited  here- 
tofore. 

At  the  autopsy  an  agar  and  a  bouillon  culture  were  inoculated  from  each  pleural 
sac.  In  all  four  tubes  only  swine-plague  bacteria  appeared  on  following  day. 

From  spleen  and  liver,  agar  and  bouillon  tubes  inoculated,  the  former  with  a  plati- 
num needle,  the  latter  with  a  particle  of  pulp.  On  the  agar  surfaces  a  small  number 
of  isolated  colonies  appeared,  made  up  of  swine-plague  bacteria.  In  the  bouillon 
tubes,  besides  the  clumps  of  swine-plague  bacteria,  a  large  spore-bearing  bacillus  ap- 
peared in  bottom  of  tubes. 

No.  13.  October  28.  Black  female  pig  weighing  28  pounds.  Died  last  night.  Sub- 
cutaneous inguinal  glands  enlarged,  firm,  pale  red,  mottled  with  gray. 

Mucosa  of  stomach  slightly  discolored  in  fundus,  otherwise  normal.  In  duodenum 
mucosa  dark  bluish  in  color,  minute  vessels  injected  and  occasionally  ruptured. 

Contents  of  large  intestine  a  brownish  liquid.  Slight  pigmentation  and  injection 
of  vessels,  no  ulceration. 

Liver  tissue  rather  firm  to  the  touch.  On  the  surface  of  the  right  half  yellowish- 
gray  spots,  involving  from  one  to  several  lobules,  about  one  to  a  square  inch!  Over 
the  entire  surface  are  disseminated  minute  dots  bf  a  red-lead  color,  each  situated  in 
the  center  of  an  acinus.  Bile  thick  and  flaky. 

Spleen  much  enlarged,  flabby  ;  pulp  dark  red. 

In  the  left  lung  the  dependent  half  of  ventral  lobe  solid,  grayish  red,  faintly  mot- 
tled on  the  surface.  Bronchioles  filled  with  plugs  of  thick  inuco-pus.  In  the  central 


42 

portion  of  the  principal  lobe  two  small  hepatized  foci.  Numerous  lung  worms  in  ter- 
minal bronchus. 

In  the  right  lung  between  ventral  and  cephalic  lobes  a  portion  of  hepatized  mot- 
tled lung  tissue.  Somewhat  back  of  this  region  a  mass  of  necrotic  tissue,  separated 
from  the  surrounding  tissue  by  a  greenish-white  line  and  covered  by  a  thick  opaque 
pleura  of  the  same  color.  In  the  principal  lobe  a  large  wedge-shaped  mass  of  hepa- 
tized tissue  extending  inwards  from  the  lateral  border  several  inches.  On  section  it 
is  dark  red,  mottled  with  grayish  circles  and  irregular  lines.  The  pleura  much  thick- 
ened, opaque.  Another  wedge-shaped  hepatized  mass  situated  near  caudal  tip,  per- 
haps further  towards  necrosis  than  the  preceding  one.  Pleura  covering  it  necrosed. 
Lung  worms  in  the  terminal  bronchus  imbedded  in  mucus. 

Cover-glass  preparations  from  the  more  recent  pneumonic  masses  show  very  few 
germs.  From  the  right  pleural  cavity  a  bouillon  and  an  agar  tube  inoculated.  In 
the  former,  motile  hog-cholera  bacilli ;  in  the  latter  about  seven  colonies  of  the  same 
size  composed  of  motile  bacilli,  probably  hog  cholera,  though  they  appear  somewhat 
too  large.  A  black  rabbit  inoculated  in  subcutis  with  a  particle  of  lung  tissue  died 
in  seven  days.  At  the  place  of  inoculation  the  subcutis  is  infiltrated  over  an  area  of 
several  square  inches  with  pus.  No  peritonitis ;  spleen  large,  containing  many  hog- 
cholera  bacilli ;  necroses  in  liver. 

In  cover-glass  preparations  from  spleen  and  liver  a  considerable  number  of  hog- 
cholera  bacilli  detected.  From  spleen  an  agar  and  a  bouillon  tube  were  inoculated 
with  platinum  needle.  Both  contain  only  hog-cholera  bacilli  on  following  day. 
Cultures  from  the  spleen  gave  the  same  result. 

The  lesions  found  in  these  thirteen  cases  may  be  summarized  briefly 
as  follows : 

No.  1.  October  12.  Extensive  hepatization  of  Inngs  with  necrotic  foci ;  lung 
worms  ;  exudative  pleuritis  and  pericarditis.  Congestion  aud  necrosis  of  stomach ; 
hypersemia,  pigmentation,  and  ulceration  of  the  large  intestine;  ulcers  small,  ulcer- 
ation  evidently  follicular.  Only  swine-plague  bacteria  found. 

No.  2.  October  12.  Spleen  large.  Fully  four-fifths  of  lungs  hepatized,  with  necro- 
tic foci;  pleuritis  and  pericarditis;  lung  worms;  bronchitis.  Small  ulcers  in  large 
intestine.  Only  swine-plague  bacteria  found. 

No.  3.  October  12.  Spleen  large.  Pneumonia  slight ;  no  pleuritis.  Hemorrhagic 
inflammation  of  stomach.  Ulcers  in  large  intestine.  Both  hog-cholera  and  swine- 
plague  bacteria  detected. 

No.  4.  October  14.  Multiple  pneumonic  foci  in  lungs.  No  pleuritis.  Lung  worms. 
HyperjBQiia  of  stomach.  Ulcers  and  patches  of  necrosis  in  large  intestine.  Only 
hog-cholera  bacilli  detected. 

No.  5.  October  15.  Scattering  pneumonic  areas ;  bronchitis ;  lung  worms.  Ulcers 
in  large  intestine  (button  ulcers).  Only  swine-plague  bacteria  detected. 

No.  6.  October  15.  Considerable  hepatization  of  all  lobes ;  lung  worms.  Large 
ulcers  in  large  intestine.  Only  hog-cholera  bacilli  detected. 

No.  7.  October  15.  Spleen  large.  Hepatization  not  extensive;  pleuritis;  bron- 
chitis; no  lung  worms.  Only  Peyer's  patch  near  valve  ulcerated.  Only  swiue-plague 
bacteria  found. 

No.  8.  October  17.  About  four-fifths  of  lung  tissue  hepatized,  with  necrotic  foci; 
pleuritis  and  pericarditis.  Lung  worms.  No  ulcers  in  large  intestine.  Infarcts  in 
kidneys.  Only  swine-plague  bacteria  found. 

No.  9.  October  18.  About  one-half  of  lung  tissue  hepatized  with  necrotic  foci ; 
pleuritis;  lung  worms;  bronchitis.  Necrotic  patches  and  ulcers  in  stomach  aud 
large  intestine.  Spleen  large.  Both- hog-  cholera  and  swine-plague  bacteria  detected. 

No.  10.  October  19.  Spleen  large.  Three-fourths  of  lung  tissue  hepatized,  with 
necrotic  foci;  pleuritis;  bronchitis;  lung  worms.  Ulceration  of  stomach  and  large 


43 


intestine  as  extensive  as  in  No.  9.  Both  swine-plague  and  hog-cholera  bacteria 
present. 

No.  11.  October  22.  Scattering  pneumonic  foci,  with  extensive  necrosis;  pleuritis; 
pericarditis;  lung  worms.  Congestion  of  stomach.  Small  number  of  ulcers  in  large 
intestine,  pigmentation.  Hog-cholera  and  swine-plague  bacteria  present. 

No.  12.  October  25.  Anterior  (cephalic)  half  of  lungs  hepatized.  Extensive  pleur- 
itis and  pericarditis;  lung  worms.  Pigmentation  of  mucosa  of  large  intestine.  Few 
ulcers  in  large  intestine  ;  follicles  with  purulent  contents.  Only  swine-plague  bac- 
teria present. 

No.  13.  October  28.  Pneumonia  not  extensive ;  pleuritis ;  bronchitis ;  lung  worms. 
Intestines  pigmented  ;  no  ulceration.  Only  hog-cholera  bacilli  found. 

In  all  there  was  pneumonia  more  or  less  extensive,  associated  in  the 
majority  of  cases  with  cejlular  and  fibrinous  pleuritis,  more  rarely  with 
pericarditis.  In  the  hepatized  regions  necrotic  masses  were  frequently 
met  with.  Bronchitis  was  common ;  lung  worms  were  very  abundant. 
The  lesions  of  the  digestive  tract  varied  from  case  to  case.  In  some  the 
mucosa  of  the  stomach  was  hyperaemic,  bordering  on  hemorrhage ;  in 
others  diphtheritic  and  ulcerated ;  in  still  others  quite  unchanged.  The 
lesions  of  the  large  intestine  ranged  from  hyperaamia  and  pigmenta- 
tion to  the  most  extensive  destruction  of  the  mucous  membrane.  Of 
the  intermediate  stages  may  be  mentioned  tumefaction  of  follicles,  with 
discharge  of  purulent  contents  and  subsequent  formation  of  small 
ulcers. 

The  results  of  the  bacteriological  work  may  be  tabulated  as  follows : 


No. 

Spleen. 

Liver. 

Lunga. 

Pleura. 

Pericardium. 

Remarks. 

1 

2.. 
3.. 

4 

do  

Hog  cholera  .  . 

do         

Swine  plague  . 
Hog  cholera  .. 

do  

Swine  plague. 
and     hog 
cholera. 
Hog  cholera  .. 

do  

Sterile  

Do. 

Swine    plague 
and      hog 
cholera. 

5 

Swine  plague. 

plague. 
No  hog  cholera 

6 

Ho<*  cholera   . 

(?) 

No      swine 

7 

plague. 

8 

.  .  do  

Swine  plague 

do  

Do. 

fl 

Hog  cholera 

Hog     cholera 

and  strepto- 
cocci. 
Swine  plague 

....do  

Swine    plague 

10 

and  swine 
plague. 

and     swine 
plague. 

...do  

and     hog 
cholera. 
Do. 

11 

and     hog 
cholera. 
Hog  cholera  .  . 

an  d     hog 
cholera. 
Hog  cholera  .  . 

Swine  plague 

Hog  cholera  .  . 

Do. 

1' 

Swine  plague. 

Swine  plague. 

and     hog 
cholera. 

Swine  plague. 

Swine  plague. 

No  hog  cholera. 

11 

Hog  cholera  

Hog  cholera  .  . 

Hog  cholera  .  . 

Hog  cholera  .  . 

No       swine 

plague. 

It  will  be  observed  that  in  six  cases  (Nos.  1,  2,  5,  7,  8,  and  12)  only 
swine-plague  bacteria  were  detected ;  in  three  (Nos.  4,  6,  13)  only  hog- 
cholera  bacteria,  and  in  four  (Nos.  3,  9,  10,  11)  both  were  found.  In 
general  I  would  not  place  too  much  stress  on  the  absence  of  either  kind  of 
bacteria,  because  there  is  no  reason  why  if  both  pathogenic  species  are 


44 

A 

present  they  should  not  after  a  time  invade  every  animal,  unless  the 
presence  of  one  disease,  such  as  swine  plague,  would  oppose  the  inva- 
sion of  hog  cholera  in  the  same  animal,  a  hypothesis  for  which  we  have 
no  supporting  facts.  If  we  turn  to  the  positive  evidence  we  find  that 
in  ten  out  of  thirteen  animals  the  same  virulent  swine-plague  bacteria 
were  found.  We  have,  in  other  words,  bacteria  pathogenic  in  pigs,  as 
we  shall  presently  show,  which  travel  from  animal  to  animal  and  pro- 
duce a  more  or  less  extensive  pneumonia  with  pleuritis.  These  facts 
are  in  themselves  sufficient  to  separate  swine  plague  as  a  distinct  dis- 
ease from  hog  cholera. 

In  those  cases  thoroughly  studied,  such  as  Nos.  1  and  2,  hog-cholera 
bacilli  were  probably  entirely  absent.  A  glance  at  the  table  will  show 
that  when  they  were  detected  they  were  always  found  in  the  spleen. 
In  Nos.  1  and  2  only  swine-plague  bacteria  were  found  in  the  spleen. 
The  same  may  be  said  of  No.  12.  Why  the  hog-cholera  bacilli  should 
have  been  in  these  animals  and  not  appear  in  any  of  the  numerous  cul- 
tures made  is  certainly  incomprehensible. 

Perhaps  the  best  evidence,  aside  from  inoculation,  that  swine-plague 
bacteria  are  the  cause  of  the  pneumonia  is  Reducible  from  the  bacte- 
riological examination  of  the  lungs  and  pleura.  In  only  two  later 
cases  were  hog-cholera  bacilli  obtained  from  the  pleura.  In  one  (No. 
13),  the  lung  disease  had  advanced  to  caseation,  and  it  accords  with 
former  experience  that  in  such  cases  swine-plague  bacteria  are  gone, 
and  if  hog-cholera  bacilli  are  in  the  animal  they  are  certain  to  appear 
in  these  dead  lung  masses,  and  hence  in  the  pleural  cavity.  In  those 
lungs  which  were  extensively  hepatized,  but  in  which  necrosis  had 
not  advanced  far,  the  hepatized  tissue  was  practically  a  pure  culture 
of  the  swine-plague  bacteria.  The  cause  of  the  intestinal  lesions  must 
remain  a  matter  of  doubt,  although  their  nature  combined  with  the 
presence  of  hog-cholera  bacilli  in  the  herd  would  lead  us  to  regard  them 
as  due  to  the  latter. 

As  to  the  origin  of  this  mixed  outbreak,  nothing  positive  could  be 
learned  of  the  former  history  of  the  herd.  As  it  was  made  up  of  two, 
possibly  three  lots,  it  may  be  assumed  that  one  lot  brought  one  germ 
and  another  lot  the  other.  This  hypothesis  gains  force  from  the  great 
variation  in  the  extent  and  character  of  the  lung  and  intestinal  lesions. 
Meanwhile  it  must  be  remembered  that  only  one-third  of  the  herd  came 
under  observation,  owing  to  the  rapidity  with  which  the  animals  suc- 
cumbed and  the  somewhat  tardy  information  concerning  the  outbreak 
which  reached  us. 

THE  PRODUCTION  OF  DISEASE  IN  SWINE  AND  OTHER  ANIMALS  WITH 
THE   SWINE-PLAGUE   BACTERIA  FROM  THIS   OUTBREAK. 

The  bacteriological  notes  already  given  indicate  a  virulent  variety  of 
these  bacteria,  inasmuch  as  rabbits  succumbed  to  a  subcutaneous  in- 
oculation of  a  minute  dose  within  20  hours.  The  following  tests  on 


45 

four  pigs  were  equally  striking.  The  culture  used  was  derived  from 
case  2  by  inoculating  a  rabbit  with  a  particle  of  lung  tissue.  The 
culture  from  the  spleen  of  this  rabbit  was  again  tested  about  a  month 
later  on  a  second  rabbit.  The  agar  culture  from  this  animal  was  used 
to  inoculate  six  agar  tubes.  From  these,  when  2  days  old,  the  surface 
growth  was  washed  down  into  the  condensation  water  with  sterile 
bouillon  and  the  turbid  liquid  transferred  to  a  sterile  test  tube.  With 
this  the  following  inoculations  were  made  : 

No.  272,  2  cubic  centimetres  subcutaneously,  one-half  into  each 
thigh. 

No.  273,  one-half  cubic  centimetre  into  right  lung,  through  chest- 
wall,  between  fifth  and  sixth  rib. 

No.  274, 1  cubic  centimetre  into  abdomen. 

No.  275,  1J  cubic  centimetres  into  right  lung. 

These  pigs  were  all  alike,  Essex  grade,  10  weeks  old,  and  weighed 
about  40  pounds  each.  The  inoculations  were  made  November  16,  5 
p.  m. 

No.  272  did  not  show  any  ill  effects  except  small  tumors  at  the  places  of  injection. 
It  was  killed  December  9  and  'found  normal. 

No.  273  was  very  sick  on  the  following  day.  It  breathed  with  difficulty  and  re- 
fused to  rise  and  eat.  On  the  fourth  day  there  was  some  improvement.  The  animal 
began  to  eat.  The  improvement  continued  and  on  December  2  (16  days  after  inocu- 
lation) it  had  apparently  fully  recovered.  On  this  day  it  was  killed  for  examination. 

About  100  cubic  centimetres  pale  yellow  serum  in  abdominal  cavity.  Diaphragm 
pressed  downwards  and  very  tense,  as  viewed  from  the  abdominal  side.  Lungs  ad- 
herent to  chest-wall  and  diaphragm-  Both  pleural  sacs  converted  into  large  abscess 
cavities,  the  walls  of  which  are  formed  by  the  diaphragm,  the  ohest-wall,  and  the  con- 
vex surface  of  the  lungs.  These  walls  are  very  much  thickened  and  covered  with 
a  pulpy  yellowish-white  layer  of  pus.  The  cavity  is  distended  with  a  turbid,  milky 
fluid.  Lungs  much  compressed,  along  dorsal  border  collapsed.  Small  median  lobe 
collapsed. 

Pericardium  adherent  to  heart  surface  by  means  of  fibrous  bands.  Pericardial  sac 
contains  a  small  quantity  pale  yellowish  turbid  liquid. 

Intestinal  tract  normal.  Liver  with  many  lobules  either  entirely  or  only  centrally 
congested.  Serous  surface  facing  diaphragm  slightly  roughened. 

At  this  time  no  swine-plague  bacteria  were  found  in  the  spleen,  as  the  cultures 
made  therefrom  with  particles  of  pulp  remained  sterile. 

No.  274  was  found  dead  early  next  morning,  i.  e.f  within  24  hours  after  inoculation. 

The  superficial  inguinal  glauds  much  reddened.  The  abdomen  contains  about  100 
cubic  centimetres  of  clouded,  straw-colored  serum.  The  serous  surface  of  the 
various  abdominal  organs  exposed  by  reflection  of  the  abdominal  walls  covered  with 
a  thin  layer  of  pale  yellowish,  friable  exudate,  thickest  on  the  liver.  The  exudate 
also  found  between  the  coils  of  iutestiues.  In  both  pleural  sacs  from  50  to  75  cubic 
centimetres  of  turbid  serum.  Pleuritic  exudate  on  the  ventral  third  of  the  right 
lung.  Similar  exudate  on  the  pericardium.  Lungs  normal.  Digestive  tract  normal 
so  far  as  the  mucous  membrane  is  concerned.  The  various  lymph  glands  of  thorax 
and  abdomen  slightly  reddened.  Liver,  spleen,  and  kidneys  not  affected. 

Only  the  spleen  of  this  case  was  examined  for  bacteria.  After  scorching  the  sur- 
face an  agar  and  a  bouillon  culture  inoculated  with  platinum  wire.  On  the  agar 
surface  about  100  isolated  colonies  from  1£  to  2  millimetres  in  diameter  appeared  ou 
the  following  day,  all  alike  and  so  far  as  examined  made  up  of  swine-plague  bacteria. 
The  bouillon  culture  likewise  proved  to  be  a  pure  culture  of  the  iujected  bacteria. 


46 

No.  275  became  very  sick  after  the  inoculation.  It  refused  to  get  up  and  eat,  and 
breathed  with  difficulty.  It  was  found  dead  November  19,  i.  e.,  between  2  and  3 
days  after  the  inoculation. 

Skin  not  discolored.  The  cut  subcutaneous  vessels  exude  drops  of  dark  blood.  In 
the  abdomen  a  few  elastic  threads  of  coagulated  exudate  stretched  across  coils  of  in- 
testines. 

In  right  pleural  cavity  about  100  cubic  centimetres  of  blood-stained  serum.  Lungs 
adherent  to  ribs  by  means  of  a  thick,  soft,  easily  removable  exndate.  Lobes  of  right 
lung  glued  to  each  other  and  to  pericardium  ;  they  are  not  enlarged.  The  pleura  of 
the  ventral  half  of  principal  lobe  is  converted  into  a  thick,  wrinkled,  and  bleached 
layer;  beneath  it  the  lung  tissue  is  hepatized.  The  dorsal  portion  of  this  lobe,  still 
air-containing,  covered  with  patches  and  shreds  of  exudate.  The  cephalic  and  ven- 
tral lobe  solidified,  not  enlarged;  grayish-red  on  section. 

The  left  lung  likewise  covered  in  part  with  pleuritic  exudate.  .  The  ventral  two- 
thirds  of  principal  lobe  covered  with  a  thick  pseudo-membrane  and  hepati/ed,  very 
firm;  on  section,  red,  mottled  with  gray.  The  ventral  and  cephalic  lobes  collapsed, 
covered  with  exudate,  which  extends  to  contiguous  pericardium.  (See  plate  vi). 
The  entire  diaphragmatic  portion  of  pleura  of  both  principal  lobes  and  median  lobe 
converted  into  a  wrinkled,  necrotic  mass.  Pericardial  sac  contains  much  reddish, 
turbid  fluid.  The  surface  of  the  heart  covered  with  a  whitish,  firm,  roughened  exu- 
date. 

Stomach  contracted ;  contains  a  small  quantity  of  bile-stained  liquid.  The  mucosa 
of  the  fundus  bluish-red,  swollen.  The  whole  covered  with  a  layer  of  viscid  bile- 
stained  mucus.  The  remainder  of  digestive  tract  free  from  inflammation. 

In  the  liver  the  central  region  of  acini  dark  brownish  red,  the  outer  portion  pale 
brownish. 

The  presence  of  the  injected  swine-plague  bacteria  in  the  organs  of  this  animal 
were  determined  by  the  following  cultures  : 

From  the  spleen,  in  which  no  bacteria  were  detected  under  the  microscope,  an  agar 
tube  inoculated  with  platinum  wire  and  a  bouillon  tube  by  adding  a  particle  of  pulp. 
The  bouillon  tube  became  clouded  with  swine  plague.  The  agar  tube  remained 
sterile.  A  rabbit  inoculated  subcutaueously  in  the  ear  with  a  platinum  loop  dipped 
into  the  bouillon  culture  died  within  20  hours.  In  blood  and  spleen  very  large  num- 
bers of  swine-plague  bacteria.  In  cultures  from  these  organs  only  these  germs  pres- 
ent. 

A  small  area  on  the  hepatized  left  principal  lobe  scorched,  and  a  small  particle  cut 
out  with  flamed  scissors.  From  the  serum  filling  the  cavity  thus  formed,  which  con- 
tained large  numbers  of  swiue-plague  bacteria,  one  gelatine  roll,  and  from  this  two 
agar  plates  prepared.  The  roll  remained  free  from  growth ;  also  one  agar  plate. 
On  the  other  appeared  a  large  number  of  minute  colonies  and  several  large  colonies 
of  bacillus  subtills.  The  former  were  identified  as  swine-plague  colonies.  From  the 
left  pleural  exudate  an  agar  tube  was  inoculated.  Abundant  growth  of  swine-plague 
bacteria  on  the  following  day. 

From  the  hepatized  region  of  the  left  principal  lobe  portions  were  placed  in  alco- 
hol and  subsequently  sections  prepared.  The  alveoli  and  small  air  tubes  densely 
packed  with  masses  of  cellular  exudate.  The  interlobular  tissue  distended  with  a 
network  of  fibrin  and  a  scanty  number  of  leucocytes.  In  the  contiguous,  still  per- 
vious areas,  some  air  tubes  were  occluded  with  cellular  plugs,  and  either  around  these 
or  independent  of  them  were  isolated  groups  of  alveoli  occluded  with  round  cells. 
Swine-plague  bacteria  were  present  in  enormous  numbers  both  in  the  parenchyma/ 
and  the  interlobular  tissue.  They  were  densely  and  uniformly  sprinkled  around  and 
between  the  cells,  in  some  places  forming  dense  zooghea.  They  were  much  smaller 
than  in  cultures,  being  just  visible  at  500  diameters.  (See  plate  XI,  figs.  2  and  3.) 

These  inoculations  show  that  these  bacteria  injected  subcutaneously 
have  little  or  no  effect,  but  when  introduced  into  one  of  the  large  se- 


47 

rous  cavities  severe  inflammation  is  aroused  followed  by  speedy  death. 
In  No.  275,  the  injection  into  the  right  lung  led  to  a  typical  pleuro-pneu- 
nionia  of  the  left  lung,  such  as  was  encountered  in  the  outbreak  from 
which  the  bacteria  were  isolated. 

These  bacteria  were  fatal  to  mice  and  guinea-pigs  and  to  pigeons  in 
large  doses : 

December  13. — Two  mice  inoculated  under  skin  of  back  with  a  loop  of  growth  from 
an  agar  culture  one  day  old.  Both  dead  next  morning,  with  spleen  much  swollen 
and  containing  large  numbers  of  the  inoculated  bacteria.  From  the  spleen  of  one  an 
agar  and  a  bouillon  culture  were  made.  The  bouillon  became  faintly  clouded ;  on 
the  agar  numerous  confluent  colonies  appeared.  Only  swine-plague  bacteria  detected 
in  these  cultures. 

From  the  same  culture  a  guinea-pig  was  inoculated  subcutaneously  in  the  same 
way.  The  guinea-pig  lived  12  days.  No  lesions  except  a  fatty  condition  of  liver 
found  at  autopsy.  A  tube  of  agar  to  which  2  drops  of  blood  were  added  remained 
sterile. 

At  the  same  time  two  fowls  and  two  pigeons  were  inoculated,  one  fowl  and  oue 
pigeon  with  a  loop  of  the  agar  culture  subcutaneously  and  one  fowl  and  oue  pigeon 
with  1  cubic  centimetre  of  a  peptone  bouillon  culture  one  day  old.  The  needle  of 
the  syringe  penetrated  the  superficial  muscular  layer  of  one  pectoral  muscle. 

Both  fowls  remained  well,  also  the  pigeon  inoculated  with  the  loop.  The  other 
pigeon  dead  next  d*ay.  On  the  right  pectoral  region  the  subcutis  was  infiltrated  and 
of  a  reddish-yellow  color,  the  subjacent  muscular  tissue  discolored  to  a  depth  of  one- 
fourth  to  one-half  inch.  Lungs  congested,  other  organs  normal.  In  the  blood  num- 
erous swine-plague  bacteria  giving  the  polar  stain ;  in  the  liver  very  few. 

In  April,  1891,  about  1|  years  after  these  bacteria  had  been  obtained  from  this  out- 
break, the  following  inoculations  were  made  to  determine  how  much  of  their  viru- 
lence had  been  lost  by  cultivation. 

April  13. — With  a  loop  rubbed  over  an  agar  culture  4  days  old,  a  large  gray  rabbit 
was  inoculated  by  inserting  the  loop  into  an  incision  on  the  ear  made  with  flamed 
lancet.  Eabbit  dead  next  morning.  In  blood  and  spleen  swine-plague  bacteria  in 
moderate  abundance. 

April  21. — Two  guinea-pig's  weighing  1£  pounds  each  received  a  subcutaneous  injec- 
tion of  0.075  and  0.15  cubic  centimetres  of  a  turbid  suspension  of  swine-plague 
bacteria  from  an  agar  culture  1  day  old. 

The  guinea-pig  which  had  received  the  largest  dose  died  in  26  hours.  At  the  place 
of  injection  slight  yellowish  infiltration  of  subcutis.  No  peritonitis.  In  both  pleu- 
ral  sacs  a  large  quantity  of  a  grayish,  partly  gelatinous  eifusion,  containing  immense 
numbers  of  bacteria.  Pericardial  sac  similarly  involved.  Both  lungs  dark  bluish 
red  throughout;  tissue  still  floats. 

The  other  guinea-pig  very  sick  for  several  days,  recovered,  and  was  killed  on  the 
eighth  day.  At  the  place  of  injection  a  minute  ulcerous  opening  from  which  pus 
could  be  pressed.  In  the  subcutis  considerable  rather  firm  infiltration,  surrounded 
by  patches  of  blood  extravasation.  Internal  organs  not  affected. 

VIII. 

Iii  November,  1889,  an  outbreak  of  swine  plague  came  to  the  notice 
of  the  Bureau,  which,  in  some  respects,  has  a  quite  remarkable  history. 
The  information  given  below  was  obtained  by  Dr.  Kilborne. 

An  educational  institution  near  this  city  was  in  the  habit  of  keeping 
on  its  inclosure  a  small  number  of  swine  in  pens  which  were  arranged 


48 


in  the  manner  indicated  in  the  figure.    The  slope  of  the  ground  was 
from  yard  1  to  yard  3,  and  from  yard  5  to  yard  3. 


YD.  3. 


YARD  1, 


PEN.  2. 


PEN.  3. 


YD,  4. 


PEN.  4. 


P£N.5.              YD.  5. 
_T 


In  September  a  boar,  5  mouths  old,  died  in  pen  1.  There  had  been 
no  disease  on  the  place  2  years  previous  to  this  occurrence,  and  no  recent 
purchase  of  pigs.  In  the  latter  part  of  October  ten  pigs,  2  mouths  old, 
were  purchased,  five  placed  in  pen  1,  and  five  in  pen  5.  At  this  time  a 
sow  in  pen  2  had  four  pigs,  all  of  which  died  in  a  few  days,  while  the 
sow,  although  sick  for  a  time,  recovered. 

In  pen  3  a  sow  became  sick  very  suddenly  November  8,  and  died  next 
day.  A  litter  of  seven  pigs,  7  weeks  old  and  small  f..r  their  age,  died 
within  4  days  after  the  death  of  the  sow.  Of  these,  five  came  under  our 
observation  (Nos.  1  to  5  inclusive,  of  the  autopsy  notes).  These  five, 
after  a  very  careful  examination,  proved  to  be  cases  of  swine  plague. 
While  the  recently  purchased  pigs  in  pen  1  remained  unaffected,  those 
in  pen  5  began  to  die  at  the  same  time  that  the  young  pigs  in  pen  3 
were  dying.  Thus  two  died  November  9  and  one  November  10.  One 
of  these  was  carefully  examined,  and  to  our  surprise  the  disease  was 
found  to  be  hog  cholera,  as  the  autopsy  notes  (No.  G)  clearly  show. 
The  remainder  were  taken  to  the  Experiment  Station.  At  the  same 
time  there  were  in  pen  4  two  pigs  about  5  months  old  and  one  old  sow. 
One  of  the  pigs,  sick  November  12,  was  transferred  to  the  Experiment 
Station,  where  it  was  found  dead  on  the  following  morning.  This  case 
also  was  one  of  hog  cholera  (Case  7).  By  feeding  the  viscera  of  these 
two  pigs  to  fresh  pigs  an  outbreak  of  hog  cholera  was  produced,  which 
was  subsequently  utilized  in  a  series  of  experiments  on  vaccination,  as  a 
means  of  exposing  swine  which  had  been  vaccinated  beforehand. 

On  inquiry  over  a  month  later,  we  were  informed  that  no  further 
losses  from  swine  diseases  had  been  sustained. 

In  the  following  pages  are  given  the  notes  of  the  autopsies  and 
bacteriological  examination  of  the  litter  of  small  pigs  which  died  in  pen 
3.  They  are  all  the  more  interesting  in  that  the  disease  was  swine 


49 

plague  uncomplicated  with  hog  cholera.  The  autopsy  notes  of  the  two 
hog-cholera  cases  from  pen  5  and  pen  4  are  appended,  to  complete  the 
history  of  this  remarkable  outbreak. 

November  11,  1889. — Pig  No.  1,  white  female,  weighs  about  15  pounds.  Died  last 
night.  Considerable  reddening  of  the  skin  over  the  ventral  aspect  of  the  body. 

Stomach  contains  a  small  quantity  of  a  yellowish  viscid  liquid.  Fundus  covered 
with  mucus  and  intensely  reddened  and  swollen.  In  the  large  intestine,  mucosa 
slightly  discolored  ;  in  a  few  places  somewhat  reddened.  No  necrosis  or  ulceration. 
Glands  of  the  meso-colon  enlarged,  indurated,  pale. 

About  one-half  of  both  lungs  hepatized,  the  disease  limited  to  the  ventral  or  de- 
pendent half.  The  various  lobes  adherent  to  one  another,  to  pericardium  and  dia- 
phragm by  means  of  a  thin,  papery  pseudo-membrane,  which  is  removable.  The  hepa- 
tization  is  very  firm  ;  on  section,  grayish  red  or  red  mottled  with  gray.  Near  the  roots 
of  the  lobes,  also  on  diaphragmatic  surface  of  the  lungs,  are  considerable  numbers  of 
small  necrotic  masses,  surrounded  by  a  bluish  zone.  In  the  trachea  and  bronchi,  red- 
dish froth  ;  in  the  distal  extremities  of  both  bronchi,  lungworms  imbedded  in  mucus. 

Spleen  small,  not  congested.  Liver  exceedingly  firm  to  the  touch.  Surface  not 
smooth,  owing  to  acini  slightly  projecting  above  interlobular  tissue. 

Bacteriological  examination  :  Preparations  from  hepatized  lung  tissue  contain  an 
immense  number  of  very  minute  oval  bacteria.  Those  from  the  pleural  exudate  con- 
tain a  smaller  number.  On  one  of  the  principal  lobes  the  pleura  was  scorched  over 
the  diseased  portion,  and  with  a  particle  of  tissue  from  within  the  scorched  area,  a 
gelatine  roll  A,  and  two  agar  plates  B,  prepared.  In  the  gelatine  roll  appeared,  after 
a  few  days,  a  large  number  of  barely  visible  colonies.  A  week  later,  besides  these,  a 
smaller  number  of  colonies,  4  to  5  times  larger  than  the  preceding,  had  appeared. 
Owing  to  the  large  number  of  colonies  microscopic  examination  not  successful. 
Minute  bits  of  gelatine  were  removed  at  different  intervals  with  warmed  platinum 
wire  and  transferred  to  peptone  bouillon.  In  these  tubes  only  swine-plague  germs 
appeared.  The  larger  colonies  may  have  been  streptococci,  as  they  failed  to  develop  in 
the  bouillon.  Both  agar  plates,  after  several  days,  contained  a  large  number  of  iden- 
tical quite  small  colonies,  which  were  found  to  be  swine  plague  colonies  by  micro- 
scopic examination  and  transfer  to  bouillon.  In  order  to  determine  whether  any  other 
bacteria  were  present,  two  bouillon  tubes  were  inoculated  directly  from  the  lungs,  by 
piercing  them  with  a  platinum  wire  and  transferring  this  to  the  bouillon.  In  both 
tubes  only  swine-plague  bacteria  appeared. 

A  rabbit  inoculated  at  the  same  time  with  a  particle  of  lung  tissue  died  in  5  days. 
The  subcutaneous  tissue  over  abdomen  extensively  thickened  by  a  purulent  and  gel- 
atinous infiltrate  extending  over  part  of  thorax.  The  abdominal  walls  are  thickened 
and  glued  to  the  viscera.  These  latter  covered  wit  h  a  rather  firm  elastic  exudate,  which 
dips  down  between  the  coils.  The  serosa  is  sprinkled  with  punctiform  ecchyruoses. 
Spleen  small ;  thoracic  organs  not  affected.  In  the  abdominal  exudate  are  immense 
numbers  of  oval  bacteria,  staining  rather  feebly.  These  not  detected  in  spleen  and 
blood.  An  agar  tube  inoculated  from  the  spleen  contained  but  a  single  swine-plague 
colony.  A  gelatine  culture  from  the  blood  shows  in  the  track  of  the  needle  about 
12  minute  round  colonies.  In  a  bouillon  culture  from  the  peritoneal  exudate  only 
swine-plague  bacteria  developed. 

From  the  pleural  exudate  of  the  pig  an  agar  and  a  bouillon  tube  inoculated  at  the 
autopsy.  In  the  former  a  considerable  number  of  isolated  and  confluent  colonies  of 
swine-plague  bacteria  appeared.  The  bouillon  culture  likewise  contains  only  swine- 
plague  bacteria. 

From  the  spleen  pulp,  in  which  no  bacteria  were  detected,  a  particle  placed  in  an 
agar  and  a  bouillon  tube.  Both  were  sterile  on  the  following  day.  On  the  third  day 
faint  cloudiness  of  the  bouillon,  which  contained  only  swine-plague  germs.  In  the 
agar  tube  the  condensation  water  was  clouded,  and  a  grayish  membrane  starting  from 
it  ascending  along  agar  surface.  Only  swine-plague  bacteria  detected  in  this  growth. 
1614 4 


50 

Portions  of  lung  tissue  from  different  lobes,  hardened  in  alcohol,  were  examined. 
Sections  from  recently  affected  lung  tissue,  bordering  on  normal  tissue,  showed  the 
alveoli  to  he  filled  in  some  lobules  with  blood  corpuscles  and  fibriu ;  in  others  there 
was,  in  addition,  a  filling  up  of  scattered  alveoli  with  round  cells.  In  still  others  the 
alveolar  capillaries  were  greatly  distended  with  corpuscles,  almost  occluding  the  al- 
veoli. Imbedded  in  the  fibrinous  plugs  of  the  alveoli  were  colonies  of  minute  cocci, 
almost  every  alveolus  containing  one  or  more  such  colonies.  la  sections  from  tissues 
in  more  advanced  stages  there  were,  in  addition  to  the  more  dense  cell  infiltration, 
,  large  masses  of  the  minute  bacteria  occupying  the  alveoli  in  some  portions  of  the 
section.  Any  regularity  in  the  distribution  of  these  bacteria  not  observed. 

No.  2.  Examiued  at  the  same  time.  White  female,  weight  15  pounds.  Skin  on 
ventral  aspect  of  body  moderately  reddened.  Subcutaneous  inguinal  glands  hy- 
perasmic. 

Stomach  contains  a  small  quantity  of  turbid  liquid.  Mucosa  of  fundus  consider- 
ably reddened.  lu  the  small  intestine  the  vessels  of  villi  appear  injected,  especially 
in  duodenum.  In  the  csecura  and  colon  the  entire  mucosa  has  an  intense  purplish  hue, 
shading  into  a  wine  color.  This  most  marked  in  the  caecum  and  upper  4  or  5  inches 
of  colon,  where  the  epithelium  appears  necrosed.  The  inflammation  gradually  dimin- 
ishes and  disappears  in  the  rectum. 

Exudative  pleuritis  as  in  case  1 ;  the  pseudo  membrane  as  thick  as  heavy  paper. 
About  two-thirds  of  right  lung  hepatized.  The  cephalic  and  ventral  lobe  entirely 
solidified,  also  adjoining  half  of  the  principal  lobe.  In  the  caudal  portion  of  the  latter 
several  hepatized  foci.  Lung  worms  in  terminal  bronchus.  The  tip  of  cephalic  lobe 
completely  necrosed.  The  ventral  lobe  contains  large,  yellowish-white,  homogeneous 
foci  of  dead  tissue.  Median  lobe  completely  hepatized.  Through  it  are  disseminated 
necrotic  foci. 

In  left  lung,  principal  lobe  entirely  hepatized.  Hemorrhagic,  grayish-red,  and 
grayish  lobules  found  on  the  same  cut  surface.  Ventral  and  cephalic  lobes  merely 
congested.  Pericardium  thickened. 

Spleen  small,  pulp  darker  than  normal  and  softened.  Liver  as  in  No.  1.  Bile  very 
thick,  dark-colored. 

Bacteriological  examination :  An  agar  and  a  bouillon  tube  were  inoculated  each 
with  a  particle  of  spleen  pulp.  The  agar  tube  remained  sterile.  The  bouillon  be- 
came faintly  clouded  on  the  second  day  and  contained  only  swine-plague  bacteria. 

The  hepatized  lung  tissue  and  pleural  exudate  both  show  presence  of  swine  plague 
germs ;  the  lung  tissue  contains  immense  numbers  of  them.  With  a  bit  of  the  latter 
a  gelatine  roll  A  and  agar  plate  B  prepared.  In  the  gelatine  roll,  a  considerable 
number  of  very  minute  brownish  colonies  appeared  within  a  week.  They  were  all 
alike.  Several  transferred  to  bouillon  at  intervals  and  the  resulting  cultures  care- 
fully examined.  Only  swine-plague  bacteria  detected.  The  agar  plate  had  a  moder- 
ate number  of  colonies,  those  growing  on  surface  from  2  to  3  millimetres  in  diameter. 
These  also  proved  to  be  swine  plague  when  examined  and  transferred  to  bouillon  for 
further  identification. 

At  the  autopsy  an  agar  and  a  bouillon  tube  were  inoculated  from  the  right  pleural 
cavity.  On  the  agar  appeared  a  large  number  of  isolated  and  confluent  colonies  all 
apparently  alike.  Some  of  these,  as  well  as  the  growth  in  the  condensation  water, 
were  examined  and  found  to  be  swine-plague  bacteria.  The  bouillon  contained  also 
a  streptococcus  and  a  bacillus,  imparting  a  sour  smell  to  the  culture.  A  rabbit  in- 
oculated with  a  particle  of  lung  tissue  died  in  6  days.  The  subcutaneous  infiltra- 
tion and  the  peritonitis  precisely  as  in  the  rabbit  inoculated  from  No.  1.  The  spleen 
contained  scarcely  any,  the  blood  few,  and  the  peritoneal  exudate  an  immense  number 
of  swine-plague  bacteria.  Agar  cultures  from  exudate  and  blood  and  a  bouillon,  cul- 
ture from  the  exudate  contained  only  swine-plague  bacteria. 

The  presence  of  swine-plague  bacteria  on  the  inflamed  mucosa  of  caecum  was  dem- 
onstrated by  inoculating  a  rabbit  with  a  particle  of  mucosa  which  had  been  washed 


51 

in  sterile  water.  Babbit  died  in  2  days  with  considerable  local  infiltration,  bnt  no 
peritonitis.  An  agar  culture  from  spleen  with  platinum  needle  remained  sterile.  A 
bouillon  culture  from  blood  became  clouded  with  swine-plague  bacteria.  To  further 
test  this  germ,  one-eighth  cubic  centimetre  of  this  bouillon  culture  7  days  old  was 
injected  subcutaueously  into  a  rabbit.  It  lived  11  days.  There  was  extensive  puru- 
lent infiltration  of  the  snbcutis  over  abdomen  and  thorax.  Internal  organs  normal. 
But  one  (bouillon)  tube  inoculated  with  particle  of  liver  tissue.  This  remained  clear. 

No.  3  examined  on  same  day.     White  female  weighing  18  pounds.     Died  last  night. 

Ventral  aspect  of  body  considerably  reddened.  Stomach  as  in  preceding  cases. 
Mucosa  of  duodenum  very  much  reddened ;  the  remainder  of  the  small  intestine  nor- 
mal. Mucosa  of  caecum  and  colon  not  quite  so  intensely  inflamed  as  in  No.  2.  Indi- 
cations of  a  yellowish,  soft  exudato  appearing  in  small  masses  as  part  of  the  feces. 
Its  microscopic  characters  not  determined. 

Double  exudative  pleuritis,  the  exudate,  thick  on  diaphragm  which  firmly  adheres 
to  lungs,  verjr  slight  on  convex  surface  of  lungs  where  it  appears  as  a  roughening  or 
a  very  delicate  membrane.  The  various  lobes  glued  to  each  other  and  to  pericardium. 

In  the  left  lung  the  two  smaller  lobes  (ventral  and  cephalic)  in  a  condition  of  pale- 
red  hepatization ;  very  slightly  enlarged.  In  the  principal  lobe  four  or  five  foci  of 
dark-red  hepatization  imbedded  in  normal  tissue,  on  section  marked  with  grayish, 
irregular  lines.  These  masses  are  elevated  slightly  above  the  surrounding  tissue  and 
covered  with  a  thick,  opaque,  greenish- white  pleura.  In  the  right  lung  both  smaller 
lobes  hepatized,  larger  than  the  corresponding  left  lobes,  very  firm  to  the  touch.  The 
cut  surface  sprinkled  with  minute  grayish  masses.  In  the  principal  lobe  the  hepa- 
tized masses  are  dark  red  in  color.  The  small  median  lobe  enveloped  ia  exudate  and 
hepatized,  the  cut  surface  grayish  red. 

In  the  bronchi  a  small  quantity  of  reddish,  frothy  liquid.  In  the  right  terminal 
bronchus  lung  worms.  Bronchial  glands  very  large,  firm,  yellowish  white. 

Pericardium  inflamed,  opaque.  In  left  heart  a  firm  washed  clot  imbedded  in  a 
dark,  soft  coagulum.  The  right  heart  distended  with  a  dark,  soft  coagulum. 

Spleen  small,  dark-colored.     Liver  and  bile  as  in  No.  2. 

Bacteriological  examination:  From  the  spleen  an  agar  and  a  bouillon  tube  inoc- 
ulated with  a  particle  of  pulp.  After  several  days  a  grayish  growth,  spreading  from 
bit  of  spleen,  composed  of  rather  large  cocci.  The  bouillon  tube  at  this  time  also 
clouded ;  contains  only  swine-plague  germs. 

Two  similar  cultures  prepared  from  the  liver.  In  the  bouillon  tube  only  swine- 
plague  bacteria  appeared.  On  the  agar  surface  three  colonies  present,  one  of  these 
a  chroniogene,  the  others  large  spore-bearing  bacilli.  In  the  turbid  condensation 
water  the  same  large  bacilli  and  swine-plague  bacteria  intermingled.  In  cover-glass 
preparations  from  spleen  and  liver  no  germs  could  be  detected. 

From  the  right  pleural  cavity  an  agar  and  a  bouillon  tube  inoculated.  Both  re- 
mained sterile. 

From  the  most  recently  hepatized  lung  tissue,  which  contains  large  numbers  of 
swine-plague  bacteria,  a  gelatine  roll  A  and  an  agar  plate  B  prepared.  In  the  gelatine 
roll  colonies  appeared  answering  to  the  description  given  for  those  under  case  I. 

The  bouillon  tubes  prepared  from  the  colonies  contained  no  hog-cholera  germs  at 
any  time.  Swine-plague  bacteria  and  possibly  streptococci  were  present,  although 
this  is  somewhat  doubtful.  The  agar  plate  B  remained  free  from  growth.  A  bouil- 
lon tube  iuocculated  with  a  platinum  needle  thrust  into  the  hepatized  lung  remained 
sterile. 

A  rabbit  inoculated  with  a  particle  of  lung  tissue  succumbed  to  the  disease  in  8 
days,  with  extensive  subcutaneous  purulent  infiltration  over  abdomen.  No  peritoni- 
tis. Cover-glass  preparations  and  cultures  from  blood  and  spleen  are  negative. 

From  this  lung  sections  were  cut  from  portions  of  one  principal  lobe  hardened  in 
alcohol.  The  alveoli  were  nearly  all  occluded  by  round  cells,  among  which  in  a  cer- 
tain number  of  alveoli  large  masses  of  the  very  minute  swine-plague  bacteria  could 


52 

be  detected.    The  small  air  tubes  likewise  filled  with  densely  packed  cell  masses,  The 
interlobular  tissue  in  a  state  of  inflammatory  oedema. 

November  12. — No.  4,  small  female,  weighing  about  twenty  pounds.  Died  last 
night.  Ventral  surface  of  the  body  moderately  reddened.  Considerable  quantity  of 
subcutaneous  fat.  Lymphatic  glands  in  groin  slightly  enlarged  and  reddened. 

One  ulcer  at  base  of  left  lower  front  tooth.  Stomach  contracted  and  contains  a 
small  quantity  of  liquid  resembling  tomato  juice.  The  mucosa  of  fundus  over  an  area 
3  inches  in  diameter  of  a  dark  wine-red  color  ;  the  hyperyernia  extends  through  entire 
mucous  layer.  On  the  surface  a  very  delicate,  easily  removable  pseudo-m<Xnbrane. 
Mucosa  of  duodenum  pigmented  and  bile-stained.  In  lower  ileum  some  patches  of 
punctiform  ecchymosis.  In  large  intestine  feces  adhering  rather  firmly  to  mucosa, 
which  is  reddened  and  pigmeuted  in  spots  and  patches  and  somewhat  rough  to  the 
touch. 

In  thracic  cavity  lungs  covered  with  false  membrane  and  in  part  adherent  to  chest- 
wall  and  pericardium.  On  removing  them,  the  pleuritis  and  hepatization  found 
nearly  as  extensive  as  in  the  preceding  case,  i.  e.,  the  greater  part  of  both  small  lobes 
in  each  lung  hepatized  and  exceedingly  firm  ;  in  the  principal  lobes  disseminated  foci 
of  hepatization  both  of  the  grayish-red  and  the  hemorrhagic  type.  Lung  worms  not 
detected.  In  the  air  tubes  of  the  ventral  lobes  cylinders  of  whitish  pus.  In  the  large 
bronchi  reddish  frothy  liquid.  Pericarditis  as  in  preceding  case.  On  the  epicardium 
a  very  delicate  pseudo-membrane. 

Liver  tissue  very  firm  to  the  touch ;  bile  thick.  Pyramidal  portion  of  kidneys  dark 
red.  Spleen  small,  somewhat  darker  colored  than  in  normal  condition. 

Bacteriological  examination :  Cover-glass  preparations  of  the  pleural  exudate  show 
a  moderate  number  of  swine-plague  bacteria.  In  the  lung  tissue  there  are  immense 
numbers  of  these  bacteria,  with  an  occasional  large  bacillus  amongst  them.  From  the 
right  pleural  cavity  an  agar  and  a  bouillon  tube,  from  the  left  an  agar  tube  inoculated 
at  the  autopsy.  In  these  tubes  a  considerable  number  of  identical  colonies  appeared 
made  up  of  swine-plague  bacteria.  In  the  condensation  water  of  an  agar  culture 
from  right  pleura  occasional  streptococci  to  be  seen.  The  bouillon  tube  became  uni- 
formly clouded  with  swine-plague  bacteria.  After  two  weeks  a  few  very  large  colo- 
nies of  strange  bacteria  had  developed  in  both  agar  tubes. 

With  a  particle  of  lung  tissue  a  gelatine  roll  A  and  an  agar  plate  B  prepared.  Roll 
A  broke ;  plate  B  showed  in  a  few  days  about  50  colonies,  evidently  alike.  Those 
examined  and  transferred  to  bouillon  consisted  only  of  swine-plague  bacteria. 

A  rabbit  inoculated  with  a  particle  of  lung  tissue  remained  unaffected.  Another 
rabbit  received  a  subcutaneous  injection  of  one-eighth  cubic  centimetre  bouillon  from 
au  agar  colony  of  lung  plate.  This  rabbit  died  in  13  days  with  a  very  large  abscess 
at  the  point  of  inoculation. 

In  the  spleen  of  pig  no  bacteria  were  detected  with  the  microscope.  In  the  liver 
several  germs  resembling  swine-plague  bacteria  were  observed.  With  particles  of 
liver  and  spleen  tissue  two  agar  and  two  bouillon  tubes  were  inoculated.  Only  the 
bouillon  tube  from  the  liver  became  fertile  and  contained  a  diplococcus ;  no  swine- 
plague  bacteria. 

Sections  from  the  lung  tissue  hardened  in  alcohol  and  stained  in  various  ways  weie 
carefully  examined.  In  the  same  section  were  lobules  in  which  the  alveoli  contained 
fibrin  and  very  few  cells,  others  in  which  much  desquamation  of  the  epithelial  cells 
had  taken  place,  and  others  in  which  the  alveoli  were  occluded  by  dense  cell  masses. 
In  some  places  the  septa  had  apparently  disappeared  and  a  continuous  plug  of  densely 
massed  cells  extended  through  a  number  of  continuous  alveoli.  The  small  air-tubes 
were  likewise  filled  up  with  cell  masses.  The  interlobular  tissue  distended  with 
serum,  the  lymph  channels  similarly  distended  and  containing  masses  of  leucocytes. 
In  all  alveoli  excepting  those  containing  only  the  desquamated  cells,  the  very  minute 
oval  swine-plague  bacteria  are  present  in  immense  numbers,  disseminated  singly 
through  the  cedematous  tissue  and  in  large  zoogkea  amongst  the  cellular  masses. 


53 

November  13. — No.  5,  small  white  male,  weight  about  10  pounds.     Died  last  night. 

In  the  digestive  tract  of  this  case  nothing  abnormal  excepting  a  somewhat  bluish 
coloration  of  the  mucosa  of  large  intestine  and  swelling  of  the  solitary  follicles,  the 
contents  of  which  can  be  expressed  through  a  central  opening. 

About  one-third  of  the  entire  lung  tissue  hepatized.  The  disease  involves  the  ven- 
tral third  of  all  the  lobes,  excepting  the  left  cephalic,  which  is  free  from  pneumonia. 
The  median  lobe  completely  solidified  and  containing  two  necrotic  foci.  A  thick 
pseudo-membrane  covers  the  pleura  of  the  diseased  areas.  In  the  bronchi  and 
branches  of  the  principal  lobes  numerous  plugs  of  lung  worms  imbedded  in  mucus. 
The  bronchi  of  the  ventral  lobes  occluded  by  cylindrical  masses  of  mucus  and  pus. 

Bacteriological  examination  :  An  agar  tube  inoculated  from  the  right  pleural  cav- 
ity at  the  autopsy  contained  subsequently  5  colonies  of  swine-plague  bacteria. 

Cover-glass  preparations  of  .diseased  lung  tissue  show  large  numbers  of  pus  corpus- 
cles, amongst  these  small  oval  bacteria,  probably  swine  plague,  and  occasional  chains 
of  streptococci.  A  gelatine  roll  culture  A  and  an  agar  plate  B  were  made  from  par- 
ticles of  lung  tissue.  In  roll  A  there  appeared,  after  a  week,  about  one  hundred  colo- 
nies of  bacillus  coli,  twelve  colonies  of  a  slowly  liquefying  chromogene,  and  a  very  large 
number  of  colonies  just  showing  a  disk  under  the  microscope.  Particles  of  gelatine 
containing  these  minute  colonies  were  removed  to  boullion,  but  no  development  took 
place.  On  the  agar  plate  about  ten  colonies  of  swine- plague  bacteria  appeared,  which 
grew  quite  large,  owing  to  isolated  position.  Transferred  to  a  boullion  their  swine 
plague  nature  confirmed. 

With  a  particle  of  lung  tissue  a  large  black  rabbit  inoculated.  Dead  in  five  days. 
The  subcutis  was  extensively  infiltrated  and  thickened  as  in  previous  cases.  Peri- 
tonitis absent.  Spleen  barely  enlarged.  In  cover-glass  preparations  from  spleen  and 
liver  no  bacteria  observed.  In  an  agar  culture  from  blood  thirty  swine-plague  colo- 
nies appeared.  After  a  week  a  fleshy,  whitish  growth  composed  of  large  motile  bacilli 
starts  from  condensation  water  upwards  on  agar  surface.  In  an  agar  culture  from 
the  liver-a  considerable  number  of  swine-plague  colonies  appeared.  In  a  bouillon 
culture  from  spleen  only  swine-plague  bacteria  developed. 

With  particles  of  spleen  pulp  of  the  pig  an  agar  and  a  bouillon  tube  inoculated.  The 
bouillon  became  very  turbid,  greenish,  fluorescent  and  contained  a  small  motile  bacil- 
lus. Plate  cultures  from  this  proved  the  bacillus  a  liquefying  fluorescent  bacillus. 
In  the  agar  tube  a  growth  started  from  particle  of  spleen  down  the  inclined  surface 
and  subsequently  imparted  to  the  agar  a  greenish  tint.  The  same  bacillus  as  that 
found  in  the  bouillon  culture  present.  No  swine  plague  bacteria  detected. 

In  all  five  pigs  specimens  of  trichocephalus  were  attached  to  mucosa  of  cajcum  and 
upper  colon. 

The  following  tables  give  a  brief  summary  of  the  facts  obtained: 

Pig  No.  1.  November  11,  one-half  of  lungs  hepatized  ;  some  uecrotic 
foci.  Exudative  pleuritis,  pericarditis.  Lung  worms.  Catarrhal  inflam- 
mation of  stomach.  Only  swine  plague  bacteria  present. 

Pig  No.  2.  November  11,  two-thirds  of  lungs  hepatized;  many  necrotic 
foci.  Pleuritis,  pericarditis.  Lung  worms.  Hypersemia  of  stomach. 
Intense  hypenemia  of  large  intestine. 

Pig  No.  3.  November  11,  one-half  of  lungs  hepatized ;  pleuritis:  peri- 
carditis; lung  worms;  hyperaemia  of  stomach  and  large  intestine. 

Pig  No.  4.  November  12,  one-half  of  lungs  hepatized;  plenritis  and 
pericarditis ;  bronchitis ;  hypersemia  of  stomach,  of  large  intestine 
slight. 

Pig  No.  5.  November  13,  one-third  of  lungs  hepatized;   pleuritis; 


54 


bronchitis ;  lung  worms ;  swelling  of  solitary  follicles  of  large  intes- 
tine, contents  expressible. 


£ig 

No. 

Lungs. 

Pleura. 

Spleen. 

Liver. 

Intestines. 

1 
2 

Swine  plague  
..  .do  _.  

Swine  plague  
...do  

Swine  plague  . 
..  .do  



Swino  plague. 

3 

..  do    

do  

4 

.  .do  

Swino  plague  and 

5 

Swine  plague,  bac. 
coli,  chromogene. 

streptococci. 
Swine  plague  

...do  

...do  

It  will  be  observed  that  these  five  animals  died  of  swine  plague  pure 
and  simple.  Hog-cholera  bacilli  were  absent.  An  examination  of  the 
pathological  notes  shows  in  every  case  extensive  pneumonia,  accom- 
panied by  exudative  pleuritis  and  terminating  in  some  cases  in  necrosis 
of  lung  tissue.  Perhaps  the  most  instructive  feature  of  the  disease 
is  the  inflammation  of  the  stomach  and  large  intestine,  which  was 
especially  marked  in  the  second  case.  In  the  third,  besides  the  intense 
hypersemia,  there  was  evidence  of  exudation. 

That  such  intense  hypersemia,  provided  the  bacteria  continue  to  act 
on  the  membrane,  or  provided  they  are  of  the  proper  degree  of  viru- 
lence, may  lead  to  croupous  and  diphtheritic  deposits  and  subsequent 
ulceration,  needs  no  comment.  Moreover,  the  swelling  of  the  solitary 
follicles  with  discharge  of  contents,  as  observed  in  No.  5,  may  lead  to 
subsequent  ulceration.  It  is  interesting  to  note  that  the  disease  reached 
its  severest  expression  in  No.  2,  both  as  regards  lungs  and  intestines, 
and  in  later  cases  the  lesions  became  less  extensive. 

The  table  giving  the  results  of  the  bacteriological  work  shows  a  grad- 
ual disappearance  of  the  swine-plague  bacteria  and  the  invasion  of  other 
bacteria.  Thus,  in  the  spleens  of  Nos.  1,  2,  and  3,  swine-plague  bacteria 
were  detected  while  the  cultures  from  the  spleens  of  Nos.  4  and  5  re- 
mained sterile.  That  these  bacteria  perish  very  speedily  in  the  body 
is  highly  probable  when  we  bear  in  mind  that  they  die  very  rapidly  in 
culture  media,  a  fact  to  be  pointed  out  further  on. 

The  swine-plague  bacteria  causing  this  outbreak  were  not  so  virulent 
as  those  of  the  preceding  one  as  demonstrated  by  the  inoculation  of 
rabbits  from  lung  tissue  and  pure  cultures.  While  those  of  the  pre- 
ceding outbreak  destroyed  rabbits  in  20  hours,  these  were  fatal  in  from 
2  to  13  days,  according  to  the  size  and  age  of  the  rabbit.  The  following 
inoculation,  made  about  4  weeks  after  the  last  case  was  examined,  serves 
as  an  additional  illustration  : 

December  6,  1889. — A  large  white  rabbit  inoculated  subcutaneously  on  right  ear 
with  a  loop  rubbed  over  the  growth  of  an  agar  culture.  The  animal  was  found  dead 
December  10.  From  the  place  of  inoculation  on  the  right  ear,  suppuration  had  ex- 
tended down  over  the  muscles  of  the  neck.  In  right  pleural  sac,  on  pleura  of  ribs 
and  right  lung,  a  thick  creamy  deposit.  A  similar,  more  consistent  exudate  on  epi- 
cardium,  which  is  more  or  less  ecchymosed.  Other  organs  not  affected. 


55 

After  constant  cultivation  of  this  germ  for  a  year  and  a  half  on  agar, 
it  had  lost  its  virulence  to  a  large  extent,  so  that  subcutaneous  inocu- 
lation produced  merely  a  local  abscess.  While  small  doses  injected  into 
the  circulation  failed  to  kill  a  rabbit  larger  doses  were  still  rapidly  fatal. 

March  31,  1891. — A  rabbit  receives  under  the  skin  of  abdomen  0.2  cubic  centimetre 
of  a  bouillon  culture  prepared  from  an  agar  culture  one  day  old.  The  rabbit  sub- 
sequently seemed  slightly  ill,  but  recovered.  It  was  chloroformed  on  the  thirteenth 
day.  Over  an  area  several  inches  square  the  subcutis  is  thickened  by  purulent  in- 
filtration, and  the  skin  gangrenous  and  very  dry  and  hard.  The  abdominal  muscles 
slightly  ecchymosed.  Internal  organs  not  affected. 

April  13. — Large  white  rabbit  receives  into  ear  vein  0.3  cubic  centimetre  of  a  bouil- 
lon culture  24  hours  old.  The  rabbit  showed  signs  of  slight  illness  for  a  time.  It 
began  to  grow  thin,  and  after  several  weeks  it  was  noticed  to  move  with  great  diffi- 
culty. Chloroformed  on  the  nineteenth  day.  Very  anaemic  and  thin.  Internal 
organs  pale  but  normal,  excepting  kidneys,  of  which  cortex  is  fatty.  Several  ab- 
scesses under  the  fascia  of  the  left  knee  joint,  containing  a  bluish  milky  pus.  Gland 
in  right  axilla  converted  into  an  abscess. 

April  29; — From  an  agar  culture  4  days  old  a  turbid  suspension  of  the  condensation 
water  was  injected  into  an  ear  vein  of  two  rabbits;  one  received  one-fourth  cubic 
centimetre,  the  other  one-half  cubic  centimetre. 

Both  very  quiet  and  drowsy  on  the  following  day;  breathing  accelerated;  one 
with  head  drawn  backward. 

May  1. — Both  dead  this  morning.  In  the  first  animal  the  head  partially  drawn 
backwards  on  neck.  Spleen  dark,  large,  and  softened.  No  peritonitis.  Liver  very 
pale;  on  left  lobes  much  interlobular  pale  yellowish  mottling.  Cloudy  swelling  of 
cortex  of  kidneys.  Fatty  degeneration  of  heart  muscle.  Right  heart  distended 
with  dark,  partly  coagulated  blood  ;  in  left,  a  small  quantity.  Both  lungs  oedema- 
tons  ;  right  hypostatic.  In  spleen  and  blood  a  moderate  number  of  bacteria  showing 
polar  stain  very  clearly.  Cultures  from  spleen  and  blood  contain  only  the  injected 
bacteria. 

In  the  second  rabbit  same  position  of  head.  Peritonitis  indicated  by  a  viscid  exu- 
date  on  ca3cum  and  stretching  between  coils  of  intestine  when  these  are  separated. 
On  liver  and  spleen  a  pseudo-membrane.  The  exudate  consists  of  endothelium  in 
state  of  fatty  degeneration,  strands  of  fibrin,  leucocytes  and  large  numbers  of  bac- 
teria showing  polar  stain.  Spleen,  liver,  kidneys,  and  blood  contain  no  bacteria 
visible  in  cover-glass  preparations.  Liver  and  kidneys  hyperaemic.  Heart  in  dias- 
tole. Both  sides  contain  dark,  partly  coagulated  blood ;  heart  muscle  fatty. 
Lungs,  especially  ventral  portions,  congested.  Cultures  the  same  as  in  preceding 
case. 

While  there  existed  the  difference  in  pathogenic  power  between  the 
bacteria  of  this  and  the  preceding  outbreak,  none  could  be  detected 
from  a  biological  and  morphological  standpoint. 

The  question  naturally  arises,  why  should  such  attenuated  bacteria 
as  these  produce  such  a  severe  disease1?  The  age  of  the  infected  ani- 
mals probably  will  answer  this  question.  Observers  have  not  infre- 
quently noted  the  fact  that  bacteria  sufficiently  attenuated  to  be  harm- 
less to  old  animals  prove  fatal  to  the  young.  The  Pasteur  school  lias 
made  use  of  this  observation  in  increasing  the  virulence  of  pathogenic 
bacteria  by  first  passing  them  through  young  animals.  It  is  claimed 
that  after  a  number  of  inoculations  these  bacteria  become  fatal  to  older 
animals  as  well. 


56 

Having  thus  demonstrated  an  outbreak  of  pure  swine  plague  among 
the  animals  in  pen  3,  let  us  turn  briefly  to  the  diseased  swine  in  the 
other  pens  which  came  under  observation.  It  will  be  remembered  that 
one  pig  from  pen  5  died  November  10,  and  was  taken  to  the  Experiment 
Station,  where  it  was  kept  in  the  refrigerator  until  November  11.  The 
subject  is  sufficiently  important  to  warrant  the  reproduction  of  the  notes : 

No.  6.  Stomach  contracted  ;  contains  a  small  quantity  of  food.  One  ulcer  at  tbe  mar- 
gin of  the  cesophageal  expansion,  the  latter  covered  with  a  thin  brownish-yellow  layer 
of  desquamated  epithelium.  In  the  ileum  small  ulcers,  about  2  to  a  square  inch,  one- 
eighth  inch  across;  adherent  slough  stained  yellow.  Extensive  ulceration  in  caecum 
and  upper  colon.  The  ulcers  vary  from  one-eighth  to  one-half  inch  in  diameter,  black- 
ish on  the  surface.  The  base  consists  of  a  firm  yellowish- white  tissue  extending  into 
muscular  coat.  Six  inches  below  the  valve  one  large,  button-shaped  ulcer,  the  firm 
base  extending  to  serosa  and  three-eighth  inch  think.  The  serosa  under  it  discolored 
and  the  meso-colon  adherent  to  it.  In  the  lower  colon  are  a  large  number  of  circular 
pale  spots  on  the  discolored,  pigmented  mucosa,  representing  probably  the  places  to 
which  exudates  had  been  attached  but  now  shed. 

Lymph  glands  in  lesser  omentum  and  meso-caecnm  with  cortex  hemorrhagjc. 

In  left  pleural  cavity  large  patches  of  blood  extravasation  under  pleura  of  ribs. 
No  pleuritis.  Posterior  mediastinal  and  bronchial  glands  hemorrhagic.  Throughout 
the  entire  lung  tissue  are  disseminated  hepatized  foci  of  various  sizes  surrounded  by 
healthy  and  more  or  less  emphysematous  tissue.  Thus  in  the  right  lung  about  one- 
half  of  both  cephalic  and  ventral  lobes  and  a  small  volume  of  principal  lobe  involved. 
In  tbe  left  lung  one-half  of  cephalic  lobe  and  tip  of  ventral  lobe  hepatized:  in  the 
principal  lobe  six  small  foci.  One-half  of  median  lobe  hepatized.  The  small  air 
tubes  plugged  with  thick  muco-pus.  In  the  principal  lobe  several  of  the  foci  directly 
traceable  to  plugs  of  lung  worms,  which  are  very  abundant. 

Spleen  somewhat  enlarged,  discolored  ;  pulp  soft. 

Bacteriological  examination:  In  spleen  pulp  a  considerable  number  of  hog-cholera 
bacteria  detected.  An  agar  and  a  bouillon  tube  inoculated  with  platinum  wire.  In 
the  former  a  considerable  number  of  isolated  colonies  of  the  same  size  appear,  which 
are,  so  far  as  examined,  hog-cholera  bacilli.  In  the  bouillon  tube  only  hog-cholera 
bacilli  observed.  A  rabbit  inoculated  with  a  particle  of  spleen  pulp  died  in  4  days. 
At  the  point  of  inoculation  a  small  abscess.  Spleen  large,  dark,  softened  :  contains  a 
a  few  hog-cholera  bacilli.  Numerous  very  small  points  of  necrosis  on  liver  surfaces. 
In  an  agar  culture  from  the  spleen  only  hog-cholera  bacilli  detected. 
•  With  a  particle  of  lung  tissue  in  which  a  few  hog-cholera  bacilli  were  observed  a 
gelatine  roll  A  and  an  agar  plate  B  prepared.  In  the  roll  there  were  present  at  end 
of  a  week  a  large  number  of  small  brownish  colonies  and  about  fifty  several  times 
larger.  By  carefully  removing  the  smaller  ones  to  bouillon  these  were  found  to  be 
hog-cholera  bacilli.  The  large  colonies  not  examined.  On  the  agar  plate  a  consider- 
able number  of  vigorous  hog-cholera  colonies  appeared  in  2  days. 

Case  7.  November  13.  Large  white  female,  5  months  old,  weight  65  pounds.  Ven- 
tral aspect  of  body  and  ears  bluish  red.  Subcutaneous  fat  abundant.  Lymphatic 
glands  of  groin  with  surface  purplish  aud  parenchyma  mottled  red  and  gray.  A 
small  number  of  ecchymoses  on  abdominal  side  of  diaphragm.  Spleen  very  large, 
blackish,  soft. 

Stomach  partly  filled  with  food.  Mucosa  of  fundus.  aud,  in  fact,  of  fully  one-third 
the  whole  area  of  stomach  surface,  intensely  reddened.  The  hyperaniia  extends  to 
subumcous  tissue.  Slight  ecchymosis  and  pigmentation  of  duodenum.  Occasional 
petechise  in  ileum;  Peyer's  patch  near  valve  pigmented.  Entire  mucosa  of  cjecura 
aud  colon  purplish  gray  and  dotted  with  petechise.  On  mucosa  of  caecum  about  30 
pale  circular  spots  slightly  depressed,  which  evidently  were  the  seat  of  adherent 
sloughs  or  exudates.  In  rectum  petechia; ;  glands  of  meso-colon  hemorrhagic. 


57 

Iu  the  principal  lobe  of  left  lung  a  bright  red  hepatized  mass  about  three- quarters 
of  au  inch  in  diameter;  in  the  right  corresponding  lobe  a  mass  half  as  large.  .In 
the  bronchi  of  these  lobes  very  many  lung  worms  and  a  considerable  quantity  of  red- 
dish gelatinous  mucus.  No  other  hepatization  and  no  pleuritis  observed.  On  the 
surface  of  the  lungs  a  few  petechiic.  The  location  of  the  hepatizations  makes  it 
probable  that  lung  worms  were  the  original  cause. 

Liver  shows  marked  post-mortem  changes.  Kidneys  with  cortical  portion  dotted 
with  numerous  hemorrhagic  points.  Clots  of  blood  surrounding  papillae. 

In  the  spleen  were  observed  hog  cholera  and  large  bacilli.  In  an  agar  culture  with 
wire  numeruos  hog  cholera  colonies  appeared. 

It  is  a  remarkable  fact  that  there  should  be  two  diseases  of  different 
nature  in  adjoining  pens  at  about  the  same  time.  It  is  not  improbable 
that  hog  cholera  was  brought  with  the  ten  pigs,  but  in  this  case  it  is 
quite  curious  that  those  in  pen  1  were  not  attacked.  We  must  as- 
sume that  perhaps  but  one  pig  was  chronically  infected  (old  ulcers)  and 
that  this  pig  placed  in  pen  5  formed  the  starting  point  of  a  slowly  de- 
veloping infection  among  the  others. 

IX. 

In  July,  1890,  the  attention  of  the  Bureau  was  called  to  an  outbreak  of 
swine  disease  of  a  very  fatal  character  about  2  miles  northwest  of  Pleas- 
antville,  New  Jersey.  Veterinarian  F.  L.  Kilborne  visited  this  locality 
July  21  and  obtained  the  following  information  from  Mr.  Joseph  Young, 
the  owner  of  the  diseased  herd,  who  gave  us  all  the  facilities  in  his 
command  for  the  investigation  of  this  plague. 

On  May  9,  1890,  Mr.  Young  bought  forty-five  pigs,  2£  to  3  months  old, 
collected  by  a  dealer  from  several  counties.  May  23,  a  second  herd  of 
fifty-two  pigs  was  obtained  from  the  same  source.  In  this  lot  were 
noticed  several  unthrifty  animals,  and  coughing  was  heard  up  to  the 
time  of  the  appearance  of  the  disease.  About  July  1  they  began  to  die, 
one  of  the  unthrifty  ones  being  the  first  to  succumb.  Deaths,  at  first 
few  in  number,  increased  until  the  number  reached  from  three  to  eight 
per  day.  Thus  from  July  1  to  July  19  thirty-four  perished.  On  July 
20  four  died,  on  July  21  seven  died,  on  July  22  eight  died. 

No  swine  had  been  on  this  farm  for  several  years  except  four  animals, 
which  had  been  raised  and  fattened  last  season  and  which  had  always 
been  in  good  health. 

The  herd  was  watered  from  -a  well,  the  waste  being  permitted  to 
run  into  a  little  depression  or  wallow  in  a  dry  sandy  soil.  The  food 
consisted  of  slops,  brought  over  from  Atlantic  City  in  boats.  Several 
other  herds  in  the  neighborhood  were  being  fed  in  the  same  way  with- 
out any  untoward  results  at  the  time.  It  should  be  stated,  however, 
that  later  several  other  herds  in  the  neighborhood  became  infected. 
This  information  did  not  reach  us  until  after  the  disease  had  died  out. 

The  symptoms  noted  by  the  observant  owner  were  coughing,  loss  of 
appetite,  and  occasional  vomiting.  The  animals  strayed  into  bushes 
and  other  hiding  places,  soon  became  lean  and  gaunt  and  weak  in  the 


58 

hind  quarters.  They  died  3  to  5  days  after  showing  signs  of  disease. 
Some  lived  longer,  others  died  quite  suddenly. 

Of  the  forty-two  pigs  remaining  July  23,  twenty  died  between  July 
23  and  July  28,  five  died  on  the  Experiment  Station,  and  only  seven,  out 
of  a  total  of  ninety-seven,  lived  through  the  disease, 

Seventeen  animals  came  under  our  observation.  Of  these,  twelve 
were  examined  on  the  farm  and  the  remaining  five  sent  alive  by  express 
to  the  Experiment  Station.  Here  they  all  died  within  a  week  after  their 
arrival.  Of  those  examined  on  the  farm,  Nos.  1  to  4,  inclusive,  and 
Nos.  11  and  12,  came  under  Dr.  Kilborne's  observation.  From  Nos.  5 
to  10,  inclusive,  cultures  were  made  on  the  farm  by  the  writer.  Cul- 
tures were  therefore  made  from  eleven  cases  only. 

The  bacteriological  examination  of  Nos.  5  to  10,  inclusive,  can  not  be 
regarded  as  thorough,  owing  to  the  innumerable  insect  pests  on  the 
farm.  Much  work,  however,  was  bestowed  upon  Nos.  13  to  17,  inclu- 
sive, which  died  at  the  Station.  The  notes  of  this  outbreak  are  reported 
in  detail,  while  the  usual  summary  will  be  given  farther  on. 

No.  1.  July  21,  1890.  Weight  of  animal  about  50  pounds.  Skin  not  reddened.  A 
few  delicate  fibrils  of  exudate  stretching  over  coils  of  intestines.  Spleen  very  much 
enlarged,  congested. 

Digestive  tract.  Stomach  contains  a  small  quantity  of  food.  Mucosa  of  fuudus 
intensely  hyperaemic,  bordering  on  hemorrhage. 

Small  intestine  nearly  normal.  Contents  of  large  intestine  liquid.  The  mucosa 
of  csecnm  and  entire  colon  nearly  concealed  by  a  layer  of  dirty,  greenish-yellow,  d  iph- 
theritic  membrane,  quite  readily  scraped  away,  exposing  a  deeply  reddened,  raw 
surface. 

Right  lung  normal.  The  entire  left  lung  is  covered  with  a  pale  yellowish  (friable) 
exudate,  which  glues  this  lung  to  surrounding  parts.  The  lung  itself  contains 
masses  of  hepatized  tissue,  aggregating,  perhaps,  one-fourth  of  the  entire  lung. 

The  lymphatic  glands  generally  are  enlarged ;  the  cortex,  and  sometimes  medul- 
lary portion  also,  infiltrated  with  blood.  Other  viscera  not  markedly  changed. 

No.  2.  July  21,  1890.  Weight  of  animal  about  75  pounds.  Died  very  suddenly 
during  the  day.  No  skin  lesions.  Spleen  barely  larger  than  normal. 

Digestive  tract.  Only  the  large  intestine  was  markedly  affected.  The  mucosa 
extensively  pigmented  with  occasional  patches  of  hyperaemia.  In  colon  just  below 
the  valve  one  ulcer  one-half  inch  across  and  a  few  smaller  ones  discovered. 

Each  pleural  sac  contained  nearly  500  cubic  centimetres  of  slightly-clouded  serum 
containing  large  masses  of  gelatinous  coagula.  The  lungs  free  from  pneumonia. 

Lymphatic  glands  and  remaining  viscera  not  diseased. 

No.  3.  July  22.  Weighs  about  40  pounds  ;  died  during  the  night.  Had  been  sick 
at  least  a  week  according  to  statement  of  owner.  Spleen  moderately  gorged  with 
blood. 

Digestive  tract.  The  mucosa  of  caecum  and  upper  half  of  colon  more  or  less  pig- 
mented and  beeet  with  rather  deep  ulcers  from  one-eighth  to  one-third  inch  in 
diameter. 

Fully  three-fourths  of  the  right  lung  is  hepatized  and  contains  a  few  necrotic 
caseous  masses.  The  pleura  of  this  lung  covered  with  considerable  pale  yellowish 
exudate  and  adherent  to  pericardium.  Left  lung  and  pleura  normal. 

No.  4.  July  22.  Animal  died  quite  unexpectedly  last  night.  Slight  exudative 
peritonitis.  Spleen  engorged. 

Digestive  tract.  Stomach  normal,  filled  with  food.  Mucosa  of  large  intestine 
extensively  pigmented,  merging  into  hyperaemia  in  the  lower  colon.  Numerous 


59 

elevated  button-like  ulcers  one-fourth  to  three- fourths  inch  in  diameter,  extending 
from  csecum  to  lower  colon. 

In  both  lungs  a  small  number  of  pneumonic  foci,  apparently  of  an  acute  character. 
Slight  quantity  of  pleuritic  exudate  in  the  right  pleural  sac. 

Lymphatic  glands  in  general  with  cortex  engorged  with  blood.  Petcchim  in  the 
cortex  of  kidneys,  beneath  peritoneal  covering  of  diaphragm,  stomach,  and  walls  of 
abdomen. 

No.  5.  July  22.  Pig  died  between  10  a.  m.  and  6  p.  m.;  examined  at  7  p.  m.  Super- 
ficial lymphatic  glands  of  the  groin  hypersemic  throughout;  cortex  has  a  purplish 
color.  In  the  digestive  tract  the  mucosa  of  the  fundua  of  the  stomach  involved  in 
hemorrhagic  inflammation  with  superficial  necrosis.  In  the  caecum  and  upper  colon 
the  mucosa  is  superficially  necrosed. 

In  both  pleural  sacs  a  considerable  amount  of  pale  yellow  serum.  The  interlobu- 
lar  tissue  of  the  lungs  distended  with  it.  No  hepatization.  Fatty  degeneration  of 
the  cortex  of  kidneys. 

This  was  the  first  animal  from  which  cultures  were  attempted.  A  tube  of  gela- 
tine was  inoculated  with  a  bit  of  spleen  tissue.  Subsequently  liquefaction  took  place. 
The  turbid  liquefied  mass  covered  by  a  viscid  pellicle.  The  small  bacillus  causing 
this  liquefaction  grew  in  the  same  manner  in  bouillon.  It  formed  a  viscid  surface 
membrane  very  speedily,  leaving  the  liquid  clear. 

An  agar  tube  which  was  inoculated  with  a  bit  of  spleen  tissue  remained  sterile. 
Similarly  two  agar  tub.es  inoculated  with  a  loop  of  serum  from  both  pleural  cavities 
failed  to  develop.  A  pipette  of  pleural  effusion  collected  at  the  autopsy  and  sealed 
was  examined  subsequently  at  the  laboratory.  It  contained  a  large  spore-bearing 
bacillus  and  some  short  rods  in  chains.  In  order  to  detect  the  presence  of  any  swine- 
plague  germs  in  the  serum,  a  bouillon  culture  was  also  made  from  the  serum,  in  which 
of  course  the  several  germs  developed  together.  A  rabbit  inoculated  in  the  ear  with 
a  drop  of  this  culture  remained  well.  Neither  swine-plague  nor  hog-cholera  bacteria 
were  thus  obtained  from  this  animal. 

No.  6.  Pig  killed  in  what  appears  to  be  a  dying  condition.  No  lesions  found  in 
lungs  or  digestive  tract.  Spleen  somewhat  enlarged  but  firm,  not  congested. 

From  the  spleen  of  this  animal  a  minute  bit  was  placed  in  tube  of  gelatine  and 
of  agar.  Both  remained  permanently  free  from  growth. 

From  the  liver  two  similar  cultures  were  made.  In  the  gelatine  tube  a  fungus  had 
developed  after  a  week,  but  no  bacteria.  In  the  agar  tube  large  spore-bearing  bacilli 
appeared  in  the  condensation  water. 

Neither  swine-plague  nor  hog-cholera  bacilli  were  obtained  from  this  case. 

No.  7.  White  pig,  died  in  course  of  the  day.  Examined  with  Nos.  5  and  6.  Ecchymoses 
on  adductor  muscles  of  the  thigh.  Hemorrhagic  condition  of  cortex  of  lymphatic 
glands.  Petechise  under  serosa  of  small  and  large  intestines.  Hemorrhagic  inflamma- 
tion of  serous  covering  of  ureters  and  bladder.  Cortex  of  kidneys  enlarged,  pale,  fatty. 
Lungs  and  digestive  tract  not  affected. 

A  bit  of  spleen  placed  in  a  tube  of  gelatine  and  a  tube  of  agar  failed  to  give  rise 
to  any  growth  in  these  tubes  subsequently. 

In  an  agar  tube  inoculated  with  a  bit  of  liver  tissue,  a  large  spore-bearing  bacillus 
was  found  which  grew  only  in  the  condensation  water  and  not  on  the  surface. 

No.  8.  Pig  killed  in  a  dying  condition.  Affected  with  umbilical  hernia.  The 
mucosa  of  the  large  intestine  was  deeply  pigmented,  both  lungs  extensively  hepa- 
tized.  Spleen  moderately  enlarged  A  gelatine  and  an  agar  tube  inoculated  with 
bits  of  spleen  tissue,  both  negative. 

No.  9.  Died  in  course  of  the  day  ;  examined  between  7  and  8  p.  m.  Spleen  large, 
gorged  with  blood.  Pneumonia  in  localized  regions  throughout  both  lungs.  Lung- 
worms  present.  The  mucosa  of  the  large  intestine  of  a  dark  bluish  color  with  scat- 
tering whitish  spots  of  slight  exudation.  From  this  case  only  an  agar  tube  was 
inoculated  with  a  particle  of  spleen  tissue.  On  July  24,  two  days  later,  there  had 


60 

appeared  on  the  inclined  surface  of  the  agar  about  thirty  isolated  colonies,  circular, 
slightly  convex,  \\  millimetres  in  diameter,  grayish,  translucent.  The  clear  conden- 
sation water  contained  a  flocculent  deposit.  Colonies  and  condensation  water  show 
minute  oval  cocci  apparently  identical  with  swine-plague  bacteria. 

From  these  colonies  a  peptone  bouillon  tube,  an  agar  tube,  and  a  gelatine  tube  were 
inoculated  August  25.  On  the  following  day  tbe  liquid  culture  contained  minute 
clumps  adhering  to  sides  of  tube.  Liquid  nearly  clear.  The  agar  tube  showed  a 
delicate  grayish  line  on  the  surface.  Both  tubes  contained  only  the  minute  oval 
cocci.  The  gelatine  tube  remained  free  from  growth.  To  test  the  pathogenic  nature 
of  the  germ  a  rabbit  was  inoculated  in  the  ear  from  a  colony  of  the  original  spleen 
culture  July  28.  (This  nabbit  had  been  inoculated  Jane  3  into  the  thigh  with  a 
very  attenuated  culture  of  swine-plague  bacteria  sent  to  the  laboratory.)  The  rab- 
bit died  in  2£  days.  From  the  original  inoculation  an  abscess  as  large  as  a  hen's  egg 
had  formed  on  the  superficial  muscular  layer  of  the  thigh.  Spleen  much  enlarged, 
soft.  In  stained  cover-glass  preparations  of  spleen,  liver,  and  blood  numerous  swine- 
plague  bacteria  were  detected.  A  tube  of  agar  was  inoculated  from  the  blood  and  a 
tube  of  bouillon  from  the  spleen.  On  the  following  day  a  uniform  grayish  glistening 
layer  had  appeared  on  the  agar  surface,  made  up,  so  far  as  the  microscopic  exami- 
nation could  go,  of  non-motile  oval  cocci.  The  bouillon  culture,  uniformly  clouded, 
contained  the  same  bacteria  only.  These  were  readily  identified  as  swine-plague  bac- 
teria. 

No.  10.  This  animal  died  during  the  night;  examined  at  7  a.  m.  next  morning, 
July  23.     Subcutaneous  lymphatic  glands  in  the  groin  very  large,  in  part  heinor 
rhagic.    Spleen  enlarged,  firm,  not  congested.     In  the  digestive  tract  the  mucosa  of 
caecum  is  concealed  by  a  very  thin  necrotic  layer;  mucosa  itself  purplish.     This  con- 
gestion extends  along  entire  colon  ;  meso-colic  lymphatics  hemorrhagic. 

In  thorax,  the  base  of  all  lobes  of  both  lungs  involved  in  bright  red  hepatization. 
Pleural  sacs  contain  considerable  serum  which  distends  also  the  interlobular  tissue. 
Heart  muscle  quite  pale  and  discolored  in  patches. 

A  small  number  of  tube  cultures  in  agar  and  gelatine  were  prepared  at  the  autopsy 
as  follows : 

An  agar  tube  inoculated  with  a  bit  of  spleen  tissue  showed  no  growth  on  the  fol- 
lowing day.  Condensation  water  turbid,  however,  containing  a  large  spore-bearing 
bacillus,  the  bacillus  becoming  spindle-shaped  or  nearly  spherical  when  the  spore 
fully  matured.  No  other  bacteria  detected.  On  the  second  day  a  faint  growth  had 
extended  on  the  agar  surface,  and  a  small  motile  bacillus  detected.  Agar  plates  wore 
then  made  to  isolate  this  bacillus,  which  was  quite  easily  accomplished  since  the  large 
spore-bearing  bacillus  failed  to  grow  on  plates.  The  small  bacillus  formed  grayish, 
slightly  gelatinous  surface  colonies.  It  was  actively  motile,  the  motion  being  chiefly 
a  twirl  with  little  change  of  place.  Careful  subsequent  tests  showed  it  to  be  entirely 
different  from  the  hog-cholera  bacillus  with  which  it  might  have  been  confounded. 

From  the  kidney  two  minute  bits  of  tissue  were  transferred,  one  to  a  tube  of  agar, 
the  other  to  gelatine.  The  agar  tube  contained  on  the  following  day  about  fifty  col- 
onies of  the  same  germ  found  in  the  spleen  culture  of  No.  9,  i.  e.,  swine  plague.  I» 
the  condensation  water  the  large  spore-bearing  bacillus  was  also  present,  and  a  few 
gas  bubbles  in  the  agar.  The  gelatine  tube  showed  very  slight  liquefaction  of  the 
gelatine  on  the  surface  where  the  bit  of  kidney  tissue  lay.  This  was  probably  due 
to  the  large  bacillus  which  did  not  develop  any  more  in  this  situation. 

From  the  liver  an  agar  and  a  gelatine  tube  culture  were  prepared  in  the  same 
manner. 

In  the  agar  tube  a  considerable  number  of  colonies  of  the  swine-plague  bacteria 
had  appeared  July  25.  No  other  germs  subsequently  detected.  In  the  gelatine  cul- 
ture slight  liquefaction  took  place,  owing  to  the  presence  of  an  actively  motile  bacillus 
in  chains. 

An  agar  tube  inoculated  from  the  pleural  effusion  remained  sterile. 


61 

With  the  swine-plague  bacteria  from  the  liver  a  rabbit  was  inoculated  in  the  ear 
by  pricking  the  skin  with  lancet  and  inserting  a  platinum  wire  dipped  into  a  colony 
on  agar.  Kabbit  dead  next  morning.  Inoculation  wound  on  ear  bluish  and  all  veins 
distended.  Similarly  veins  of  subcutis  filled  with  blood.  Spleen  enlarged,  con- 
gested. Liver  in  large  part  invaded  by  coccidia.  In  the  blood  and  spleen  numerous 
bacteria  detected  showing  the  polar  stain.  An  agar  and  a  bouillon  culture  from  the 
blood  and  spleen  contain  subsequently  only  the  same  germs  found  in  the  tissues. 
Bouillon  faintly  clouded,  no  clumps  present.  Agar  growth  like  that  from  case  9. 

Sections  from  the  lung  tissue  of  case  10  hardened  in  alcohol  were  stained  in  alka- 
line methylene  blue  and  alum  carmine.  The  iuterlobular  tissue  was  greatly  distended, 
containing  a  network  of  fibrin  and  very  few  cells.  Tbe  alveoli  contained  a  slight 
amount  of  fibrin  and  very  few  cells.  Throughout  the  specimens  were  individual  fila- 
ments and  bundles  of  filaments  of  a  rather  large  bacillus,  evidently  the  same  as  that 
obtained  in  one  culture.  Occasionally  in  the  contents  of  the  alveoli  were  seen  scat- 
tered bacteria  of  the  size  and  form  of  swine-plague  bacteria. 

Sections  from  a  subcutaneous  inguinal  gland  hardened  in  alcohol  and  stained  in 
alkaline  methyleue  blue  revealed  large  areas  infiltrated  with  blood  corpuscles  and 
penetrated  by  distended  blood  vessels.  In  addition  to  the  large  bacilli  found  in  the 
lung  tissue  clumps  of  very  small  oval  bacteria,  identical  in  appearance  with  swine- 
plague  bacteria,  were  found  scattered  over  the  entire  section,  the  clumps  being  largest 
in  the  hemorrhagic  area. 

In  sections  from  the  spleen  none  but  the  large  bacilli  were  detected.  The  spleen 
was  extensively  loaded  with  blood  pigment. 

The  two  following  cases  were  examined  by  Dr.  Kilborne  on  the  farm  on  the  morn- 
ing of  July  28.  Both  had  succumbed  during  the  night.  No  bacteriological  examina- 
tion was  made,  but  the  notes  are  given  to  show  the  extreme  variation  in  the  lesions 
of  this  outbreak. 

No.  11.  Subcutaneous  inguinal  glands  very  large,  hemorrhagic  on  section.  Spleen 
very  large,  dark,  friable.  Mucosa  of  fundus  of  stomach  very  hyperaemic.  Numerous 
petechije  in  mucosa  of  small  intestine.  Mucosa  of  large  intestine  intensely  con- 
gested, portions  almost  hemorrhagic  ;  depressed  ulcers  on  Peyer's  patch  near  valve, 
covered  with  a  thin  slough ;  one  is  over  one-half  inch  in  diameter.  In  the  upper  colon 
are  large  branny  patches  of  superficial  necrosis,  besides  numerous  smaller,  round 
points  of  necrosis.  The  various  abdominal  lymph  glands  with  very  hyperaemic 
cortex. 

In  thorax  both  pleural  sacs  contain  100  cubic  centimetres  of  clouded  serum.  The 
costal  Jind  pulmonary  pleura  covered  with  a  yellowish,  friable,  membranous  exudate, 
causing  mutual  adhesion  of  the  various  lobes.  Pericardial  sac  not  invaded.  The 
major  portion  of  both  lungs  hepatized,  only  the  principal  lobes  being  in  part  still 
pervious.  Hopatized  lobes  dark  red.  Bronchial  glands  hemorrhagic. 

No.  1'2.  Peritonitis  indicated  by  the  presence  of  100  to  150  cubic  centimetres  of 
serous  exudate  in  abdominal  cavity.  Some  few  fibrils  of  coagulated  lymph  stretched 
over  intestines;  extensive  serous  effusion  between  layers  of  meso-colon.  Spleen 
affected  like  that  of  No.  11,  though  less  markedly  so. 

Stomach  contains  about  a  litre  of  food  ;  mucosa  pale  and  covered  with  abundant 
tenacious  mucus.  Slight  ecchyinosis  of  upper  duodenum.  In  lower  duodenum  and 
some  feet  in  length  of  jejunum  the  walls  infiltrated  with  extravasated  blood  to  twice 
the  normal  thickness.  Mucosa  of  a  deep  red  color  and  partly  covered  by  patches  of 
friable  yellowish  exudate  readily  removable.  Considerable  blood  in  lower  small 
intestine  with  slight  ecchymosis  of  mucosa. 

Mucosa  of  large  intestine  more  or  less  pigmented.  In  caecum  are  three  ulcers  one- 
fourth  to  one-half  inch  in  diameter,  the  subjacent  tissue  being  thickened  by  infiltra- 
tion from  one-half  to  three-fourths  inch.  On  Peyer's  patch  near  valve,  and  in  upper 
and  middle  colon,  are  about  half  a  dozen  similar  large  depressed  ulcers  with  very 
thick  base,  and  some  smaller  ones. 


62 

In  the  lungs  the  cephalic  and  ventral  lobes  are  involved  in  pale  red  hepatization 
•without  pleurisy. 

The  abdominal  and  thoracic  lymph  glands  more  or  less  hemorrhagic  throughout 
their  substance. 

The  following  five  sick  animals  were  sent  by  express  to  the  Experi- 
ment Station  of  the  Bureau  July  28.  They  reached  the  Station  next 
day  and  were  placed  in  a  disinfected  pen. 

No.  13  dies  July  31,  3  p.  m. ;  placed  in  refrigerator  until  August  1.  Weighs  about 
30  pounds.  Skin  on  ventral  aspect  of  body  more  or  less  reddened ;  over  the  ster- 
num a  few  excoriations.  The  enlarged  inguinal  glands  show  as  lumps  under  the  skin. 
On  section  they  present  a  mottled  gray  and  red  surface,  the  red  limited  chiefly  to 
the  cortex.  (Edema  of  the  snbcutis  over  right  knee. 

False  membrane  covers  the  left  half  of  the  mass  of  intestines  and  the  spleen  ;  con- 
sists of  an  elastic,  rather  firm  yellowish  white  layer.  Spleen  firmly  glued  to  the 
surrounding  intestines,  slightly  enlarged,  dark,  softened.  Liver  firm,  cuts  with  con- 
siderable difficulty.  Kidneys  in  condition  of  parenchymatous  degeneration.  One 
hemorrhagic  spot  in  medullary  portion  of  one  kidney.  Pelvis  contains  a  whitish 
glairy  liquid. 

Digestive  tract.  Two  superficial  necroses  on  the  inner  surface  of  lower  lip  in  front, 
one  on  the  upper  lip  and  on  edge  of  tongue  near  tip.  Stomach  contains  a  little 
deeply  bile-stained  fluid.  Mucosa  sprinkled  with  red  spots  of  a  washed-out  appear- 
ance, most  numerous  in  fundus  and  near  pylori c  valve.  Hypersemia  of  duodenum 
begins  sharply  at  pyloric  valve.  From  the  opening  of  bile  duct  a  few  drops  of  thick 
bile  can  be  expressed.  Remainder  of  small  intestine  not  markedly  changed.  The 
Peyer's  patch  in  lower  ileum  has  some  of  its  follicles  enlarged  from  which  caseous 
masses  can  be  expressed. 

Large  intestine  contains  much  sand  and  gravel.  Mucosa  of  cjccum  of  a  dark  slate 
color.  The  summit  of  the  folds  of  a  purplish  hue.  Free  edge  of  valve  bordered  by  a 
thin  slough.  On  Peyer's  patch  near  valve  areas  of  necrotic  tissue  of  a  yellowish  color, 
resting  on  a  firm,  yellowish-white  base  three-sixteenths  of  an  inch  thick.  Upper 
colon  has  its  mucosa  of  the  same  dark  slate  color,  merging  into  a  wine  red.  Two 
ulcers  one-eighth  of  an  inch  in  diameter  observed.  In  lower  colon  congestion  slight 
and  gradually  disappearing  towards  rectum.  A  small  number  of  circular  whitish 
erosions,  apparently  associated  with  the  solitary  follicles. 

Thorax.  Of  the  left  lung,  the  ventral  and  cephalic  lobes  are  interspersed  with 
small  regions  of  collapse.  The  remainder  of  the  lobes  very  einphysematous  and  hy- 
peraemic.  Of  the  right  lung,  the  anterior  half  (i.  e.,  including  cephalic,  ventral,  and 
adjacent  portion  of  principal  lobe)  hepatized,  covered  by  a  thin  false  membrane, 
gluing  the  various  lobes  lightly  to  each  other  and  to  chest  wall.  The  diseased  lobes 
show  tlje  regular  mottling  in  the  upper,  dorsal  portion.  As  we  proceed  towards  the 
ventral  portion  the  mottling  is  less  distinct,  the  tissue  firmer  and  interspersed  with 
small,  irregular,  necrotic  foci.  The  smaller  bronchi  contain  a  thick,  whitish  pus.  In 
ventral  lobe  a  portion  of  the  parenchyma  as  large  as  a  marble  completely  converted 
into  a  grayish-yellow  homogeneous  mass.  Of  the  principal  lobe  about  one-third  or 
one-fourth  hepatized.  The  mottling  of  surface  very  regular.  On  section  grayish, 
circumscribed  areas  one-half  inch  in  diameter  interspersed.  Over  these  masses  the 
pleura  is  converted  into  a  wrinkled,  roughened,  hide-like  membrane. 

Trachea  and  bronchi  contain  small  quantities  of  foamy  liquid  intermingled  with 
yellowish  particles.  Bronchial  glands  barely  enlarged,  firm;  some  lobules  pale, 
others  reddened. 

Bacteriological  notes.  At  the  autopsy  an  agar  tube  was  inoculated  with  a  platinum 
loop  lightly  rubbed  over  the  pleural  exudate.  On  following  day  a  thin  grayish 
growth  with  condensation  water  clouded.  Examination  of  hanging  drop  and  stained 
coverglass  preparations  shows  only  swine-plague  germs. 


63 

In  cover- glass  preparations  of  hepatized  lung  tisane  a  large  number  of  germs  re- 
sembling swine-plague  bacteria  were  seen,  also  some  other  forms.  Two  agar  platea 
were  made  from  the  lung  by  thoroughly  scorching  the  pleural  surface,  cutting  out  of 
the  scorched  area  a  bit  of  tissue  and  transferring  with  platinum  loop  the  serum  collect- 
ing in  this  minute  cavity  to  10  cubic  centimetres  sterilized  water.  With  one  loop  of 
water  10  cubic  centimetres  agar  was  inoculated  for  Plate  A.  From  this  agar  two 
loops  were  transferred  to  agar  for  Plate  B.  On  following  day  about  five  colonies  ap- 
peared on  Plate  A.  These  were  made  up  of  various  bacteria.  Plate  B  remained 
sterile.  At  the  same  time  a  bouillon  culture  was  made  from  the  lung  tissue.  In  it 
several  germs  grew.  These  were  plated.  No  swine-plague  germs  obtained. 

With  a  bit  of  hepatized  lung  tissue,  obtained  as  described  above,  a  rabbit  was  in- 
oculated subcutaneously  August  12,  2  p.  m.  The  rabbit  was  dead  next  morning  at 
8  a.  in.,  i.  e.,  in  less  than  18  hours.  In  spleen,  liver,  and  blood  preparations  numerous 
polar-stained  swine-plague  germs  present.  An  agar  culture  from  heart's  blood  con- 
tained only  swine-plague  germs. 

From  the  peritoneal  exudate  of  pig,  consisting  of  cells  and  fibrin  and  numerous 
bacteria  of  several  varieties,  two  agar  plate  cultures  were  made.  On  Plate  A  one 
large  colony  of  spore-bearing  bacilli  and  one  small  colony  of  swine-plague  germs. 
Plate  B  completely  overgrown  by  the  spore-bearing  bacillus. 

A  bouillon  culture  from  the  exudate  contains  streptococci  and  swine-plague  bacte- 
ria. Agar  plate  cultures  were  made  therefrom  and  both  germs  isolated. 

At  the  same  time  a  large  rabbit  was  inoculated  subcutaneously  with  a  bit  of  the 
exudate.  Dead  within  18  hours.  Stained  cover-glass  preparations  of  blood  from 
heart,  spleen,  and  liver  tissue  show  polar-stained  swine-plague  germs.  An  agar  cul- 
ture from  the  blood  contains  only  swine-plague  germs. 

From  the  spleen,  after  thoroughly  scorching  through  the  exudate,  two  agar  plate 
cultures  and  a  bouillon  culture  were  made  with  bits  of  spleen  pulp.  The  bouillon 
culture  contained  only  swine-plague  germs.  On  Plate  A  several  hundred  colonies 
appeared  next  day.  The  superficial  ones  from  2  to  3  millimetres  in  diameter  with  cir- 
cular, sharply  outlined,  slightly  convex  disk  of  a  grayish  glistening  appearance. 
Those  examined  were  made  up  of  swine-plague  germs.  Plate  B  remained  free  from 
growth. 

The  swine-plague  bacteria  were  thus  obtained  from  lungs,  pleura,  spleen,  and  peri- 
toneal exudate,  while  hog-cholera  bacilli,  which  were  looked  for  with  the  greatest 
care,  could  not  be  found. 

No.  14.  Died  late  August  3,  and  was  kept  in  refrigerator  until  next  morning.  Be- 
fore death  frequent,  liquid,  yellowish  discharges  were  observed. 

On  the  left  side,  extending  from  sternum  to  the  left  forelirnb,  the  subcutis  over  the 
pectoral  muscle  is  infiltrated  with  a  gelatinous  blood-stained  serum.  The  right  pec- 
toral muscle  somewhat  discolored  by  extension  of  the  process.  A  discolored,  blood- 
stained area  in  the  abdominal  muscle  on  the  left  side. 

Considerable  post-mortem  changes,  in  spite  of  the  fact  that  the  animal  was  kept 
on  ice  over  night.  Spleen  very  large,  dark,  soft :  the  tissue  surrounding  it  stained 
with  coloring  matter  of  the  blood. 

Mucosa  of  stomach  in  fundus  very  hyperremic,  partly  hemorrhagic.  The  cardiac 
expansion  covered  with  a  thin,  blackish,  removable  layer.  In  the  large  intestine  the 
lymphoid  patch  near  valve  is  partly  necrosed.  About  6  inches  below  valve  a  firm 
neoplastic  button,  about  1  inch  in  diameter  and  one-fourth  inch  thick.  In  cfocum 
and  parts  of  colon  are  numerous  small  (one-eighth  inch)  superficial  necroses.  Mueosa 
injected. 

Lungs  considerably  diseased.  Of  the  right  lung  the  ventral,  adjacent  portion  of 
principal,  and  small  median  lobe  are  hepatized.  On  the  left  side  both  cephalic 
and  ventral  are  solidified.  These  diseased  lobes  are  several  times  larger  than  the 
normal  collapsed  lung,  very  firm  and  nodular  to  the  touch.  They  are  covered  by 
shreds  and  patches  of  exudate,  gluing  the  lobes  firmly  to  each  other,  to  the  pericardium 
and  diaphragm.  The  nodular  condition  is  due  to  the  presence  of  a  large  number  of 


firm,  yellowish,   caseous  masses,  varying  from  one-fourth  to  three-fourths  inch  in 
diameter,  dispersed  through  the  hepatized  tissue. 

Bacteriological  examination  included  the  spleen,  the  lungs,  and  the  pleural  cavity. 
At  the  autopsy  an  agar  tube  was  inoculated  with  a  bit  of  pleural  exudate.  Small 
colonies  appeared  on  the  agar  surface  on  the  following  day,  some  made  up  of  what 
appeared  to  be  streptococci,  others  of  micrococci.  From  this  a  bouillon  culture  was 
prepared,  and  the  latter  plated  on  the  following  day.  From  these  paltes  a  coccus, 
growing  in  clumps  and  short  chains,  and  a  large  bacillus,  were  isolated.  At  the  same 
time  a  rabbit  was  inoculated  in  the  ear  from  the  agar  culture.  The  rabbit  died  in  11 
days.  At  the  point  of  inoculation  was  a  large  ulcer.  Spleen  small.  Cultures  from 
various  organs  on  agar  and  in  bouillon  remained  sterile. 

With  a  bit  of  hepatized  lung  tissue  a  rabbit  was  inoculated  in  the  ear.  Dead  in  8 
days.  Ulcer  at  the  point  of  inoculation.  Right  lung  hepatized.  Pleural  cavity  con- 
tains some  blood-stained  serum.  Cultures  from  this  animal  likewise  remain  sterile. 

From  a  bit  of  lung  tissue  agar  plates  were  also  made.  On  plate  A  only  two  colo- 
nies appeared  made  up  of  large  micrococci ;  on  plate  B  a  thin  grayish  growth  made 
up  of  spore-bearing  bacilli. 

From  the  spleen  two  agar  plates  were  made,  from  which  a  large  coccus  and  bacillus 
fluorescens  were  isolated.  A  bouillon  culture  made  directly  from  the  spleen  was 
also  plated  with  the  result  of  finding  a  streptococcus  and  a  large  micrococcus. 

No.  15.  Male  pig,  weight  about  35  pounds.  Died  yesterday  and  at  once  placed  in 
refrigerator  until  morning. 

On  abdomen  and  inner  aspect  of  thighs  a  few  reddish  scabs.  Spleen  somewhat  en- 
larged and  congested. 

Digestive  tract :  One  ulcer  on  tip  of  tongue.  Stomach  contains  a  small  quantity  of 
muddy  liquid.  Cardiac  expansion  of  oesophagus  covered  by  a  yellowish,  easily  re- 
movable layer  of  friable  material.  The  mucosa  dotted  with  small  red  pits.  In  fundus 
adeeply  reddened  area  of  small  extent  covered  with  a  thin  necrotic  layer.  Duodenum, 
commencing  with  pyloric  valve,  of  a  slate  color  and  deeply  pigmented  in  spots.  Pig- 
mentation and  aborescent  injection  extends  down  the  small  intestine.  In  large  in- 
testine considerable  pigmentation  of  mucosa.  In  caecum  and  upper  12  inches  of  colon 
are  a  large  number  of  extensive  ulcers  of  irregular  outline,  varying  in  length  from 
one-half  to  several  inches.  They  are  slightly  depressed  and  covered  by  ochre-yellow 
sloughs  scraped  away  with  difficulty.  The  entire  depth  of  mucosa  necrosed.  Ileo- 
csecal  valve  completely  encircled  by  a  band  of  necrosis.  Below  the  first  12  inches  of 
colon  the  necrosed  areas  are  slightly  raised  above  the  surface.  No  marked  thicken- 
ing or  infiltration  beneath  them.  In  addition  to  the  larger  patches  there  are  small, 
slightly  depressed,  round  ulcers  one-eighth  to  three-sixteenths  inch  in  diameter,  with 
adherent  superficial  slough. 

Of  the  lung  tissue,  a  portion  of  the  right  ventral,  an  adjacent  portion  of  principal 
lobe,  and  part  of  left  ventral  lobe  collapsed,  of  a  red  flesh  color ;  no  pneumonic  infiltra- 
tion perceptible.  In  the  bronchi  and  extending  into  branches  are  small  quantities 
of  translucent,  very  gelatinous  mucus.  In  the  collapsed  right  ventral  lobe  the  small 
air  tubes  contain  whitish  cylindrical  plugs  of  mucus  and  pus. 

Urine  very  turbid,  contains  much  calcic  oxalate  but  no  albumen.  Bacteriological 
examination  was  limited  to  the  lungs,  spleen,  liver,  and  kidneys. 

From  the  collapsed  lung  tissue  agar-plate  culturesSvere  made  with  a  minute  bit  of 
tissue.  Plate  A  on  following  day  contained  numerous  isolated  and  one  spreading 
colony;  the  latter  made  up  of  motile  spore-bearing  bacilli,  the  former  of  swine- 
plague  bacteria.  Plate  B  showed  but  two  grayish  flat  colonies,  composed  of  large 
cocci. 

A  rabbit  inoculated  subcutaueously  with  a  bit  of  lung  tissue  was  found  dead  on 
the  morning  of  the  second  day.  At  the  point  of  inoculation  more  or  less  extravasa- 
tion of  blood.  About  25  cubic  centimetres  of  blood-stained  serum  in  abdominal  cav- 
ity. Liver  has  a  red  clay  color.  Cultures  on  agar  and  bouillon  from  heart's  blood 
and  spleen  contain  only  swine-plague  bacteria. 


65 

Cover  glass  preparations  of  spleen  pulp  from  pig  showed  some  large  (post-mortem) 
bacilli.  On  an  agar  plate  both  swine-plague  bacteria  and  motile  bacilli  resembling 
hog  cholera  were  isolated.  These  motile  bacilli  were  carefully  studied  and  compared 
with  hog-cholera  bacilli.  The  results  are  given  farther  on.* 

From  the  liver,  in  which  a  few  large  bacilli  were  observed  in  cover-glass  prepara- 
tions, a  bouillon  and  an  agar  culture  were  prepared.  In  both  there  appeared  swine- 
plague  bacteria  and  streptococci.  These  were  isolated  on  ag;ir  plates.  A  rabbit  in- 
occnlated  from  the  bouillon  culture  by  a  prick  in  the  ear  was  dead  in  less  than  20 
hours.  On  small  intestine  numerous  ecchymoses.  Spleen  somewhat  enlarged  ;  lungs 
hypersemic.  From  blood  and  spleen  cultures  were  made  and  cover-glass  preparations 
examined.  All  showed  swine-plague  germs  and  these  only. 

From  the  kidney,  which  apparently  contained  no  bacteria,  an  agar  and  a  bouillon 
culture  were  made  with  minute  bits  of  tissue.  The  latter  remained  sterile.  The 
former  showed  flaky  masses  of  micrococci  resembling  the  swine-plague  germ  but  had 
no  effect  on  a  rabbit  inoculated  therewith.  To  test  virulence  of  the  swine-plague 
bacteria  isolated  on  agar  plates  from  lung  and  spleen,  bouillon  cultures  inoculated 
from  colonies  on  the  plates  were  injected  into  two  rabbits  subcutaueously,  each  re- 
ceiving one-eighth  cubic  centimetre.  Both  were  dead  next  day.  In  the  organs  were 
swine-plague  germs  in  large  numbers.  The  same  germs  obtained  in  culture  from 
these  rabbits. 

Gelatine  roll  cultures  made  from  these  bouillon  cultures  failed  as  usual  to  develop. 

No.  16.  Female  pig,  weight  from  75  to  80  Ibs.  Died  at  noon,  August  4 ;  examined  2 
hours  later.  General  condition  of  body  good.  On  ventral  surface  along  median 
line  and  on  left  fore-limb,  slightly  elevated  scabs  one-half  inch  in  diameter.  Ex- 
tensive serous  infiltration  of  superficial  muscular  tissue  of  ventral  aspect  of  neck 
and  sternum  and  of  muscles  under  scapula,  extending  along  the  muscles  of  the  left 
limb  as  far  as  the  toes.  The  limb  is  very  much  swollen,  the  skin  bluish  red.  Sub- 
cutaneous lymph  glands  of  groin  enlarged,  firm,  and  pale,  mottled  with  red  lines  and 
streaks. 

Spleen  enlarged,  dark,  and  soft.     The  fat  of  the  mesentery  dotted  with  petechiae. 

Digestive  tract :  One  ulcer  on  left  margin  of  tongue.  The  fundus  of  stomach  has 
its  mucosa  thrown  into  small  folds  and  deeply  reddened  over  an  area  of  about  S  inches 
in  diameter,  the  hyperaemja  being  most  intense  on  the  periphery  of  this  area.  About 
3  inches  from  the  pyloric  valve  an  area  of  necrosed  tissue  3  inches  long  and  1  inch 
wide,  the  slough  blackish,  involving  the  entire  mucous  layer  and  one-eighth  to  one- 
fourth  inch  thick.  Lymphatic  glands  on  lesser  curvature  with  hemorrhagic  cortex. 

Mucosa  of  duodenum  deeply  pigmented,  the  pigmentation  beginning  abruptly  at 
the  valve  and  extending  with  variable  intensity  throughout  the  entire  small  intestine. 
Mesenteric  glands  with  cortex  much  reddened. 

Contents  of  large  intestine  of  an  earthy  character,  more  or  less  adherent  to  the 
mucous  membrane.  Mucosa  of  c;ecum  and  colon  of  a  pale  slate  color.  In  the  rectum 
a  considerable  number  of  somewhat  faded  puuctiform  extravasations  on  a  pale  mn- 
cosa.  In  cajcum,  2  inches  from  valve,  one  ulcer,  one-half  inch  in  diameter,  with  super- 
ficial, pultaceous  slough.  On  Foyer's  patch  near  valve  one  small  ulcer.  In  the  upper 
colon  about  3  inches  from  valve,  an  irregular  patch  of  necrosed  mucosa,  about  2 
inches  long,  with  blackish  surface  and  rather  firm,  yellowish  base  one-eighth  to  one- 
fourth  inch  thick.  In  remainder  of  colon  three  superficial  healing  ulcers  with  easily 
detachable  slough. 

Liver  enlarged;  interlobular  marking  appears  broadened  and  pale,  the  center  of 
acini  dark  red.  Parenchyma  somewhat  softened  and  hyper&mie.  No  sensation  of 
grittiness  imparted  to  knife.  Much  fat  observed  in  sections  of  fresh  tissue  in  the 
form  of  large  globules.  Cells  sharply  outlined,  nucleus  distinct. 

Kidneys  show  under  capsule  a  small  number  of  petechise.  Organ  very  pale  through- 
out, especially  cortex. 

*  See  page  77. 


66 

Over  both  lungs  the  interlobular  tissue  is  distended  with  clear,  yellowish  serum, 
some  iu  pleural  sacs.  Parenchyma  oedematousj  not  hepatized,  with  exception  of  a 
necrotic  and  O3dematous  focus  near  tip  of  right  principal  lobe  adjacent  to  large  bron- 
chus, which  at  this  point  is  occluded  with  adult  lung  worms.  Trachea  and  bronchi 
contain  much  foam  and  yellowish  flakes.  Bronchial  glands  enlarged ;  some  lobules 
with  cortex  hemorrhagic,  others  mottled  red  and  pale. 

Heart  cavities  and  valves  normal.  Left  auricle  sprinkled  thickly  with  punctiform 
hemorrhages. 

Bacteriological  examination :  Two  agar  tubes  inoculated  with  a  loop  of  pleural 
serum  remained  permanently  clear. 

Agar  plates  from  the  osdematous  lung  developed  on  plate  A  about  150  colonies  of 
bacillus  fluorescens.  On  plate  B  one  similar  colony.  A  rabbit  inoculated  with  a  bit  of 
the  same  material  remained  unaffected. 

Spleen  pulp  shows  no  bacteria  on  microscopic  examination.  One  agar  plate  pre- 
pared with  a  bit  of  spleen  pulp  shows  growth  only  around  the  bit  of  tissue.  The 
growth  made  up  of  motile  bacilli  which  resemble  hog-cholera  bacilli.  The  notes  of 
the  comparative  studies  of  these  bacilli  are  reserved  for  the  end  of  this  chapter.* 

A  tube  of  bouillon  inoculated  from  the  spleen  remained  clear. 

Liver  tissue  shows  no  bacteria  on  microscopic  examination.  Two  agar  plates  pre- 
pared with  a  bit  of  tissue  remain  sterile.  A  tube  of  bouillon  inoculated  in  the  same 
manner  became  clouded  with  a  short,  thick,  non-motile  bacillus.  Agar  plates  from 
one  kidney  likewise  negative. 

Pig  No.  17  died  August  5,  in  the  morning,  and  was  examined  soon  after.  Female, 
weighing  about  40  pounds,  and  in  good  condition. 

The  subcutaneous  lymph  glands  in  the  groin  are  enlarged  and  reddened,  in  part 
hemorrhagic.  In  peritoneal  cavity,  a  considerable  quantity  of  straw-colored  serum. 
The  serosa  of  large  intestine  roughened  and  covered  by  shreds  of  exudate.  A  con- 
siderable mass  of  gelatinous  exudate  between  layers  of  mesocolou.  Mesocolic 
glands  swollen,  very  hypersemic.  Spleen  very  large,  dark  colored,  friable  (11  by  3 
by  f  inch). 

Digestive  tract :  Stomach  partly  filled  with  a  thick  pea-soup  like  liquid.  Fundus 
over  an  area  of  4  inches  in  diameter,  deeply  congested  and  swollen.  A  few  ascar- 
ides  in  stomach.  The  mucosa  of  ileum  sprinkled  with  numerous  punctiform  hemor- 
rhages. The  caecum  appears  as  an  enormously  enlarged,  dark,  bluish-gray  body,  the 
color  being  due  to  diffuse  blood  extravasations.  To  it  are  adherent  several  coils  of 
small  intestine  and  of  colon.  It  is  impossible  to  separate  these  parts,  the  adhesion 
being  due  to  extensive  inflammatory  deposits.  The  wall  of  caecum  shows  great 
thickening ;  in  several  places  it  is  1^  inches  thick.  The  mucosa  of  caecum  and 
upper  colon  sprinkled  with  large  numbers  of  ochre-yellow  excrescences  about  one- 
fourth  inch  apart,  and  from  one-eighth  to  one-half  inch  in  diameter.  These  are  read- 
ily pulled  away  from  the  membrane,  some  leaving  but  a  faint  depression,  others  a 
roughened  spot  behind,  surrounded  by  a  bluish-red  zone.  The  larger  the  excres- 
cences the  deeper  the  necrosis  beneath  them.  The  mucosa  is  in  general  of  a  dirty 
slate  color,  faintest  in  the  rectum. 

Lungs  normal  with  following  exceptions :  An  area  of  collapse  1  inch  square  in  right 
cephalic  lobe,  and  a  small  area  on  diaphragmatic  surface  of  right  principal  lobe  about 
one-half  inch  square  showing  consolidation  beneath.  Bronchial  glands  and  those  at 
base  of  heart  with  cortex  hemorrhagic.  Air  tubes  free  from  mucus  and  lung  worms. 

A  considerable  quantity  of  serum  in  heart-sac.  Epicardium  is  covered  with  a  very 
delicate  exudate  and  is  thickened  and  roughened.  Ecchymoses  on  left  auricle  and  en- 
docardium of  left  ventricle. 

Liver  not  markedly  changed ;  bile  very  thick  and  flaky.  Parenchymatous  degenera- 
tion of  cortex  of  kidneys.  Some  petechiae  on  pyramids  and  in  pelvis. 

Bacteriological  examination :    From  the  pericardia!  exudate  one  agar  and  one 

"  See  page  77. 


67 

bouillon  tube  inoculated  with  platinum  loop.  Both  remained  sterile.  Similarly 
two  tubes  inoculated  with  peritoneal  exudate  remained  sterile.  Agar  plate  cultures 
from  the  spleen  which  showed  no  germs  on  microscopic  examination  were  made  by 
adding  to  tube  A  a  bit  of  spleen  pulp,  to  B  three  loops  from  first  tube.  Plate  A  de- 
veloped one  colony  made  up  of  micrococci.  On  plate  B  one  colony  made  up  of  bacilli 
appeared.  A  bouillon  culture  made  at  the  same  time  with  bit  of  spleen  pulp  became 
clouded  and  contained  a  large  spore-bearing  bacillus  and  a  micrococcus.  This  was 
plated,  but  only  one  colony  developed  made  up  of  cocci.  A  rabbit  inoculated  at  same 
time  from  bouillon  remained  unaffected.  From  the  liver  agar  plates  remained  sterile. 

The  important  pathological  changes  found  in  these  17  cases  varied 
greatly  from  animal  to  animal.  In  some  cases  the  lungs  were  most 
severely  involved,  in  others  the  lesions  in  the  large  intestine  must  be 
regarded  as  most  important.  In  this  respect  this  outbreak  differs  very 
decidedly  from  the  two  preceding  ones,  in  which  there  was  more  or  less 
uniformity  observable.  Besides  the  respiratory  and  digestive  tracts,  the 
lyniDhatic  glands  and  the  serous  membranes  were  most  frequently  in- 
volved. In  the  glands  tumefaction  with  hyperaemia  and  hemorrhage  was 
quite  common.  In  the  lungs  the  appearance  of  the  hepatized  regions 
varied  considerably.  In  some  necrotic  changes  had  already  appeared. 
The  following  synopsis  of  the  lesions  will  serve  to  illustrate  the  state- 
ments made : 

No.  1.  July  21,  1890.  Pneumonia  of  left  lung  with  exudative  pleuritis.  Hypertemia 
of  stomach ;  diphtheritic  inflammation  of  large  intestine.  Lymphatic  glands  hyper- 
itniic  and  hemorrhagic.  Spleen  very  large. 

No.  2.  Double  serous  pleuritis.  Large  intestine  byperaemic  and  pigmeuted.  Sev- 
eral ulcers. 

No.  3.  Pneumonia  of  right  lung  with  necrotic  masses ;  pleuritis,  pericarditis.  Ulcer- 
ation  of  upper  large  intestine. 

No.  4.  Pneumonic  foci  in  both  lungs;  pleuritis.  Hyperaeinia,  pigmentation,  and 
ulceration  of  large  intestine.  More  or  less  blood  extravasation  in  lymphatics. 

No.  5.  July  22'.  Double  serous  pleuritis  with  interlobnlar  oedema  of  lungs.  No 
hepatization.  Hemorrhagic  inflammation  of  stomach ;  similar  inflammation  of  large 
intestine  with  superficial  necrosis  of  mucosa. 

No.  6.  Killed ;  examination  negative. 

No.  7.  Hemorrhagic  lymphatics ;  bubserous  hemorrhages  in  abdomen.  Lungs  and 
digestive  tract  not  affected. 

No.  8.  Extensive  hepatization  of  both  lungs  ;  pigmentation  of  large  intestine. 

No.  9.  Spleen  large.  Scatteriug  pneumonic  foci ;  lung  worms.  Hyperaemia  of  large 
intestine. 

No.  10.  Partial  hepatizatiou  of  lungs  with  interlobular  oedema  and  serous  pleuritis. 
Lymphatics  hemorrhagic.  Hyperjernia  and  superficial  necrosis  in  large  intestine. 

No.  11.  July  28.  Extensive  hepatization  of  lungs  with  double  plastic  pleuritis. 
HyperiBinia  of  stomach.  Diphtheritic  inflammation  of  large  intestine.  Lymph  glands 
hvpersemic  and  hemorrhagic. 

No.  12.  Anterior  small  lobes  of  lungs  hepatized;  no  pleuritis.  Peritonitis.  Hem- 
orrhagic inflammation  of  a  portion  of  small  intestine.  Pigmentation  of  large  intes- 
tine ;  indurated  ulcers  present.  Lymph  glands  hemorrhagic. 

No.  13.  July  31.  Partial  hepatization  of  lungs  with  necrotic  foci;  pleuritis; 
bronchitis;  peritonitis.  Hyperaamia  of  large  intestine;  ulceration  slight. 

No.  14.  August  4.  Gelatinous  oedema  of  left  fore  limb.  One-half  of  lung  tissue  hep- 
atized with  many  necrotic  foci ;  pleuritis.  Hemorrhagic  inflammation  of  stomach. 
Ulcers  in  large  intestine 


68 


No.  15.  Atelectasis  of  several  lobes  of  lungs;  no  hepatization  j  bronchitis.  Hem- 
orrhagic  inflammation  of  stomach.  Extensive  ulceration  in  large  intestine. 

No.  16.  Extensive  osdetua  of  left  fore  limb.  (Edema  of  lungs.  Serum  in  both 
pleural  sacs.  Bronchitis.  Lung  worms.  General  swelling  of  lymph  glands.  Hyper- 
ii'inia  of  stomach  with  localized  necrosis.  Pigmentation  and  discoloration  of  small 
and  large  intestines.  A  few  ulcers  in  the  latter. 

No.  17.  August  5.  Luugs  nearly  normal.  Pericarditis.  Peritonitis.  Hyperaemia 
of  stomach.  Enormous  inflammatory  thickening  of  caecum  with  deposits  around  it. 
Spleen  large.  Lymph  glands  swollen,  hypersemic. 

The  important  question  arises  as  to  the  true  nature  of  this  disease. 
To  the  writer  it  appeared  at  first  like  hog  cholera,  possibly  like  a  mixed 
outbreak  of  hog  cholera  and  swine  plague.  The  bacteriological  in- 
vestigations, however,  did  not  confirm  this  opinion,  based  on  the  post- 
mortem appearances.  As  the  investigation  proceeded  hog-cholera 
bacilli  failed  to  appear  in  the  cultures  with  certain  exceptions  to  be 
discussed  farther  on,  and  indicated  in  the  .following  table  as  motile 
bacilli : 


Case 
No. 

Lungs. 

Pleura. 

Spleen. 

Liver. 

Kidney. 

5 

Negative   .... 

Negative  

6 

do  

7 

....do  

....do    

g 

do  

9 

Swine  plague. 

10 

Negative  

Negative  

Swine  plague. 

Swine  plague 

13 

Swine 

Swine  plague. 

Swiue-plague. 

(Peritoneum) 

14 

*  plague. 
Negative  . 

Negative  

Negative  

swine  plague. 

15 

Swine 

Swine-plague 

Swine  plague  . 

16 
17 

plague. 

Negative  . 

Negative  
(Pericardium) 

and  motile 
bacilli. 
Motile  bacilli 
(bog   chol- 
era?) 
Negative  

Negative  
....do  

....do  

(Peritoneum) 

negative. 

negative. 

It  will  be  noted  that  in  the  eleven  cases  bacteriologically  examined 
swine-plague  bacteria  appeared  in  only  four.  In  these  four  cases  they 
were  detected  in  nearly  all  organs  subjected  to  examination.  Why  they 
were  not  found  in  all  cases  may  be  due  to  several  reasons.  In  the  first 
place,  former  experience  has  shown  that  swine-plague  bacteria  are  apt 
to  remain  localized,  and  that  dissemination  through  the  body  does  not 
always  take  place.  If  limited  to  the  digestive  tract  they  could  not  have 
been  detected,  because  this  was  not  subjected  to  examination.  Secondly, 
swine-plague  bacteria  are  short  lived,  even  in  cultures.  They  may  have 
largely  disappeared  from  the  body  at  the  time  of  death.  Moreover,  it 
is  not  improbable  that  many  swine  die  from  the  secondary  effects  of  the 
disease.  (See  No.  17.)  The  time  of  examination  is  therefore  of  import- 
ance. Swine  may  be  infected  all  together  within  a  short  time,  and  the  re- 
tarded deaths  may  be  due  to  partial  resistance  followed  by  complica- 
tions. The  lesions  produced  in  the  lungs  and  intestines  may  permit 
other  bacteria  to  enter  the  body,  which  complicate  still  more  our  under- 
standing of  the  real  cause. 


69 


While  therefore  the  bacteriological  results  were  meager,  the  inocula- 
tion experiments  and  one  experiment  in  which  pigs  were  exposed  to  the 
disease  were  successful  in  demonstrating  conclusively  the  pathogenic 
power  of  the  swine-plague  bacteria  obtained  from  this  outbreak. 

EXPOSURE    EXPERIMENT. 

The  experiment  in  which  healthy  station  pigs  were  exposed  to  those 
sent  from  Pleasantville  in  the  same  pen  is  particularly  interesting. 
Five  Station  pigs  (Nos.  383-387)  were  placed  in  the  pen  with  the  five 
infected  pigs  (Nos.  13-17).  The  period  of  exposure  varied  greatly,  as 
may  be  seen  from  the  table  below.  Nos.  384  and  385  received  a  thor- 
ough exposure  so  far  as  regards  contact  with  the  sick  pigs,  No.  383  a 
partial  one,  and  Nos.  386  and  387  were  placed  in  the  infected  pen  only 
after  all  the  sick  and  infected  had  died. 


No. 

July  29. 

July  30. 

July  31. 

Aug.  1. 

Aug.  2. 

Aug.  3. 

Aug.  4. 

Aug.  5. 

Bacteriological 
result. 

1? 

X 

X 

Dies 

Swine  -plague 

14 
H 

X 

x 

X 

x 

X 

x 

X 
X 

X 

x 

X 
Dies  

Dies  .  . 



bacteria. 
Negative. 
Swine-pl  ague 

16 

X 

X 

X 

x 

x 

X 

Dies  .. 

bacteria. 
Negative  (hog- 

17 

X 

X 

X 

X 

X 

X 

X 

Dies  .. 

cholera    bac- 
teria?) 
Negative. 

383 

Exposed  .  . 

x 

X 

384 
385 

Exposed.. 
.  .  do 

X 

x 

X 

x 

X 

x 

X 

x 

X 

x 

X 

x 

X 

x 

Dies  August  9  of 

386 

swine  plague. 
Exposed  Aug.  9. 

S87 

Do. 

The  result  of  this  exposure  was  the  death  of  No.  385  of  swine  plague. 
In  the  lungs  were  disseminated  numerous  hepatized  foci  undergoing 
necrosis.  There  was  considerable  plastic  pleuritis  matting  the  lobes  to- 
gether. In  the  digestive  tract  extensive  hypera3inia  bordering  on 
hemorrhage.  Swine-plague  bacteria  were  obtained  from  the  lungs, 
pleural  exudate,  heart's  blood,  and  large  intestine.  Cultures  were  also 
made  from  the  spleen,  liver,  mesenteric  glands,  and  kidneys,  to  make 
sure  that  if  hog-cholera  bacteria  were  present  they  should  not  be  over- 
looked, but  none  could  be  found.  A  clearer  demonstration  of  the  disease- 
producing  power  of  swine-plague  bacteria  could  not  well  bo  obtained. 
The  importance  of  this  case  warrants  the  publication  of  the  notes  in 
detail : 

No.  385.  Black  Essex  grade,  aged  3  months,  placed  in  pen  containing  Nos.  13  to 
17,  inclusive,  on  July  29.  Found  dead  August  9,  rather  unexpectedly,  after  a  sickness 
lasting  but  2  days,  and  manifested  by  dullness  and  refusal  to  eat. 

Examined  a  few  hours  after  death  ;  kept  on  ice  in  the  meantime.  As  the  skin  is 
reflected,  the  cut  subcutaneous  blood  vessels  discharge  drops  of  dark  blood.  In  ab- 
dominal cavity  nothing  abnormal.  Pericardium  thickened,  opaque,  vessels  injected. 
Left  half  of  heart  firmly  contracted.  Ecchymoses  on  the  right  auricle.  Right  side 
contains  a  pale  clot  imbedded  in  a  dark  coagulum. 


70 

Respiratory  tract :  Mncosa  of  larynx  and  epiglottis  congested.  Mncosa  of  trachea 
covered  with  a  very  thin  layer  of  translucent,  very  viscid  uiucus.  Bronchial  glands 
enlarged,  pinkish  ou  section.  Costal  pleura  of  the  right  side  discolored,  thickened, 
overlaid  by  a  soft  grayish  exudate  ;  its  blood-vessels  injected.  Diaphragm  similarly 
affected.  The  various  lobea  of  the  lungs  lightly  glued  to  one  another  and  to  the  peri- 
cardium. Considerable  pleuritic  exudate  on  the  right  ventral  and  along  the  edges  of 
both  principal  lobes.  Lungs  in  general  hyperaemic.  Left  cephalic  lobe  emphysema- 
tons;  left  ventral  shows  hemorrhagic  spots  near  its  tip  and  contains  two  firm  nod- 
nles,  appearing  as  yellowish  spots  under  pleura.  Left  principal  lobe  contains  four 
of  these  spots  corresponding  to  firm  nodules  in  the  parenchyma.  Besides  these,  a 
wedge-shaped,  very  firm,  hepatized  mass  extends  inward  from  the  edge  and  almost 
through  the  depth  of  the  parenchyma.  These  various  masses  appear  yellowish,  homo- 
geneous, imbedded  in  hyperaemic,  air-containing  tissue.  They  vary  from  one-eighth 
to  five-sixteenths  inch  in  diameter,  nearly  all  of  them  situated  near  the  surface.  The 
largest  ones  are  covered  by  roughened,  thickened  pleura,  thrown  into  wrinkles ;  these 
are  in  part  yellowish,  in  part  bright  red  and  pink  in  color.  The  three  lobes  of  the 
right  lung  contain  these  necrotic  masses.  There  are  several  in  the  right  cephalic, 
about  six  in  the  ventral,  and  over  a  dozen  in  the  principal  lobe,  the  largest  being 
one-half  inch  in  diameter. 

Digestive  tract:  Several  small  superficial  sloughs  on  dorsum  of  tongue,  near  tip. 
Stomach  contains  a  considerable  quantity  of  food.  Fundus  deeply  reddened  over  an 
area  5  inches  in  diameter.  Duodenum  with  its  mucosa  bluish-gray,  pigmeuted.  Pey- 
er's  patch  showing  as  an  aggregation  of  small,  depressed  pigment  spots.  Arbores- 
cent injection  of  jejunum  merging  into  a  general  hyperaemia  lower  down.  About  18 
inches  above  valve  a  patch  of  mucosa  2  inches  long,  intensely  reddened. 

Extensive  pigmentation  of  mucosa  of  caecum.  Mucous  glands  at  the  valve  dis- 
tended with  plugs.  About  12  inches  below  the  valve  the  mucosa  is  intensely  red- 
dened, merging  on  hemorrhage.  A  very  delicate  elastic  membrane  (fibrin?)  covers 
this  region,  extending  for  about  12  inches  down  the  colon.  Below  this  latter  point 
the  mucosa  continues  more  or  less  hyperaemic  and  pigmented  into  the  rectum.  Mes- 
euteric  glands  enlarged  with  cortex  and  interlobular  portions  hemorrhagic.  Meso- 
colic  glands  in  the  same  condition. 

Kidneys  with  cortex  pale,  somewhat  enlarged.  Otherwise  no  marked  changes  ob- 
served. 

Spleen  slightly  enlarged  and  softened. 

Bacteriological  examination  includes  the  following  organs: 

In  two  necrotic  foci  of  the  lungs  examined  a  number  of  minute  oval  bacteria  with 
polar  stain  were  observed  in  cover-glass  preparations.  Plates  prepared  with  a  bit  of 
this  tissue  remained  sterile,  however.  A  rabbit  inoculated  subcutaneously  with  a 
bit  of  necrosed  lung  tissue  at  3  p.  m.,  Aug.  9,  was  found  dead  next  morning.  In  the 
spleen  and  heart's  blood  and  in  cultures  therefrom  only  swine-plague  bacteria  de- 
tected. The  cultures  were  inclined  agar  and  bouillon. 

In  cover-glass  preparations  of  pleural  exudate,  a  large  number  of  swine-plague 
bacteria  were  detected.  Two  inclined  agar  and  one  bouillon  tube  inoculated  at  the 
autopsy.  One  agar  remained  sterile,  the  two  other  tubes  developed  into  pure  cul- 
tures of  swine-plague  germs. 

From  the  spleen  agar  plates  prepared  with  a  bit  of  pulp  remained  sterile.  A  bouil- 
lon culture  contained  a  large  spore-bearing  bacillus.  From  the  liver,  the  same  prep- 
arations made.  Both  plates  and  bouillon  remained  sterile. 

From  the  contents  of  right  ventricle  two  agar  and  one  bouillon  tube  were  inocu- 
lated after  scorching  through  the  wall.  The  bouillon  tube  remained  clear.  Both 
agar  tubes  contained  subsequently  a  grayish  glistening  growth  of  swine  plague 
bacteria. 

From  a  mesenteric  gland  one  agar  and  one  bouillon  tube  inoculated  by  scorching 
the  surface  and  removing  with  small  scissors  bits  from  beneath  this  area.  Both  tubes 
remained  sterile. 


71 

From  one  kidney  two  agar  plates  and  a  bouillon  tube  prepared.  Plate  A  was 
spoilt  by  an  extensive  surface  growth.  On  Plate  B  abont  12  colonies  developed, 
some  made  np  of  micrococci,  some  of  bacilli.  The  bacilli  on  plate  B  were  examined 
more  closely  and  readily  differentiated  from  hog-cholera  bacilli  (bacillus  coli  communis) 
in  gelatine  rolls  and  subcultures  therefrom.  The  bouillon  culture  contained  a  large 
spore-bearing  bacillus. 

From  the  hypenemic  mncosa  of  colon  agar  plates  were  made,  which,  however* 
gave  no  information  as  to  the  presence  of  swine-plague  bacteria.  A  rabbit  was  in- 
oculated by  injecting  under  the  skin  a  few  drops  of  scraping  from  the  colon  stirred 
up  in  sterile  water.  Rabbit  found  dead  on  the  second  morning.  In  cover-glass  prep- 
arations and  cultures  from  blood  and  spleen  only  swine-plague  bacteria  detected. 

The  four  remaining  pigs  did  not  die,  but  they  were  ill  for  a  time  and 
remained  in  a  very  unthrifty  condition.  They  were  killed  about  three 
months  after  exposure.  No  pathological  changes  were  observed  with 
the  exception  of  slight  hyperaemia  in  the  duodenum  and  a  few  small 
areas  of  collapse  in  the  lobes  of  the  right  lung  of  384,  and  bronchitis  and 
collapse  of  the  entire  right  cephalic  lobe  in  38G.  In  387  the  solitary 
follicles  of  the  colon  were -swollen;  from  some  a  curdy  mass  could  be 
expressed  through  a  central  depressed  opening. 

INOCULATION  OF   SWINE  WITH   SWINE-PLAGUE  BACTERIA  FROM  THIS 

OUTBREAK. 

Besides  the  successful  production  of  disease  by  simple  contact  with 
diseased  animals,  a  considerable  number  of  inoculations  upon  pigs  were 
made,  the  earlier  ones  to  test  the  pathogenic  power  of  these  bacteria, 
the  later  ones  in  carrying  out  vaccination  experiments.  Only  a  portion 
of  them  are  given  below  : 

On  October  30,  two  pigs  (Nos.  399  and  404)  were  fed  the  chopped  viscera 
of  six  rabbits  which  had  been  inoculated  subcutaneously  on  the  preced- 
ing day  and  had  all  succumbed  during  the  night.  The  viscera,  which 
contained  immense  numbers  of  swine-plague  germs,  were  readily  eaten 
after  being  mixed  with  a  small  quantity  of  feed.  The  pigs  remained 
well. 

On  the  same  day  the  following  inoculations  were  made : 

Pig  No.  402  received  a  subcutaneous  injection  of  5£  cubic  centimetres 
of  a  peptone  bouillon  culture  of  swine-plague  bacteria  24  hours  old, 
one-half  injected  into  each  thigh. 

No.  400  received  into  a  vein  of  the  leg  1  cubic  centimetre  of  the  same 
culture. 

No.  403  received  into  a  vein  of  the  leg  5  cubic  centimetres  of  the  same 
culture. 

No.  401  received  into  the  right  lung,  through  the  chest  wall,  5  cubic 
centimetres. 

These  pigs  were  black  pigs  (Essex  and  Berkshire  crosses)  about  3 
months  old.  The  bacteria  originally  derived  from  case  15  had  been 
passed  through  a  number  of  rabbits  and  guinea-pigs  since  August  3. 

No.  402  showed  no  signs  of  disease  after  the  inoculation.    No.  403 


72 

died  first.    The  inoculation  took  place  at  3:30  p.  m.,  October  30,  and 
the  animal  was  found  rigid  at  6:30  next  morning. 

General  blush  of  the  skin  on  the  ventral  aspect  of  the  body.  On  right  side  the 
small  vessels  of  the  subcutis  filled  with  blood  which  oozes  from  the  cut  ends  in  the 
form  of  thick  drops.  Both  superficial  inguinal  glands  hyper;cmic. 

A  small  quantity  of  yellowish  serum  in  the  abdominal  cavity.  A  network  of 
delicate  fibrils  stretching  across  coils  of  intestine.  Peritoneum  dull,  opaque  in  ap- 
pearance. 

Trachea  and  bronchi  contain  reddish  froth,  mucosa  reddened.  Punctiform  hemor- 
rhages under  the  pleura  of  left  lung.  Slight  general  oadenia  of  both  lungs;  some 
interlobular  oadema  of  the  right. 

Stomach  contains  a  moderate  quantity  of  deeply  yellow-colored  liquid.  The 
mucosa  covered  with  a  thick  layer  of  tenacious  mucus.  The  fundus  over  an  area  8 
inches  in  diameter  is  intensely  hypersemic,  the  intensity  being  greatest  in  the  center 
of  the  area.  Contents  of  duodenum  of  a  blackish  color.  More  or  less  hyperaemia 
throughout  the  small  intestine,  vrith  swelling,  hypenemia,  and  ecchymosis  of  Peyer's 
patches.  More  or  less  hyperaemia  in  patches  in  the  csecnm  and  colon.  The  glandular 
patch  at  the  valve  especially  reddened.  Feces  dry.  Follicles  show  as  circular,  red 
spots  from  the  serous  side.  Lymphatic  glands  of  the -lesser  omeutuiu,  mesentery,  and 
meso-colon  very  much  reddened. 

Liver  congested.     Bile  thicker  and  darker  than  normal. 

On  surface  and  throughout  the  cortical  portion  of  kidneys  numerous  punctiform 
hemorrhages.  Pyramids  intensely  congested.  Glands  at  hilus  with  cortex  hemor- 
rhagic.  Bladder  contracted,  empty. 

No.  401  died  in  the  evening  of  October  31,  i.  e.,  somewhat  more  than 
24  hours  after  inoculation.  It  was  placed  in  large  refrigerator  until 
next  morning. 

Subcutaneous  vessels  as  in  No.  403.  Small  patches  of  a  grayish,  viscid  exudate  on 
the  large  intestine,  liver,  and  spleen.  Punctiform  ecchymoses  barely  visible  to 
naked  eye  under  serosa  of  large  intestine.  Arborescent  injection  of  the  subserous 
vessels  on  ventral  wall  of  abdomen  and  intestines  generally. 

In  the  right  pleural  sac  a  considerable  quantity  of  blood-stained  liquid  and  shreds 
of  exudate  stretching  from  lung  to  chest  wall.  The  various  lobes  of  both  lungs 
glued  together  and  to  pericardium.  The  lateral,  ventral  border  of  both  Inngs  have 
the  pleural  covering  much  thickened,  roughened,  and  thrown  into  wrinkles.  Both 
lungs  congested  and  cedematous.  In  the  right  cephalic  lobe  a  mass  of  dark  red 
hepatized  tissue  which  may  be  the  place  where  needle  punctured.  Grayish-red 
hepatization  of  the  major  portion  of  left  cep'aalic  lobe.  Trachea  and  bronchi  contain 
a  large  quantity  of  reddish  foam.  Mucosa  with  minute  vessels  injected. 

Pericardium  opaque  and  roughened.  The  entire  epicardium  similarly  affeqted.  A 
grayish  membranous  exudate  about  the  base  of  the  heart  extending  upon  the  large 
vessels. 

Stomach  contains  a  moderate  quantity  of  turbid,  saffron-colored  liquid;  mucosa 
covered  with  a  thin  layer  of  mucus.  Punctiform  reddening  of  fuudus.  Small  intes- 
tine contains  much  yellow  liquid,  mucosa  not  altered.  Large  intestine  contains 
firm  feces.  No  lesions  observed. 

Cortex  of  kidneys  rather  pale,  pyramids  very  dark  red. 

Under  capsule  of  spleen,  some  small  extravasations.  Parenchyma  pale,  organ  not 
enlarged. 

Cover-glass  preparations  from  peritoneum  of  small  and  large  intestines  and  of  liver 
show  many  swine-plague  bacteria.  In  the  spleen  their  presence  not  determinable  on 
cover- glass  preparations.  Cultures  contained  them,  however. 


73 

No.  400  became  very  sick  on  the  day  following  the  inoculation.  It 
was  unable  to  rise  and  showed  signs  of  distress  when  disturbed.  It 
continued  to  lie  quietly  until  November  3,  when  it  died  at  noon,  about 
4  days  after  the  inoculation: 

Animal  in  very  good  condition  ;  abundance  of  subcutaneous  fat.  Blood  vessels  of 
subcutis  as  in  preceding  cases.  In  abdominal  cavity  nothing  abnormal. 

Double  pleuritis  with  adhesion  of  various  lobes  of  lungs  to  each  other,  to  chest 
wall  and  pericardium.  Grayish  membranous  exudate  over  the  ribs  on  the  right  side. 
The  subjacent  pleura  has  a  bluish  appearance.  The  corresponding  pleura  of  lung 
covered  by  patches  of  similar  exudate.  The  right  lung  dark  red  throughout  but  not 
hepatized.  In  the  left  lung  the  ventral  third  of  the  ventral  lobe  is  dark  red,  solid; 
on  section  granular  and  interspersed  with  grayish  areas.  The  lateral  edge  of  adjacent 
principal  lobe  is  likewise  hepatized  for  a  distance  of  1  inch  inward  and  2  inches  along 
border. 

Pericardium  thickened,  opaque,  roughened;  bloodvessels  injected;  entire  epicar- 
diuin  covered  with  a  rather  thick  false  membrane,  loosely  attaching  the  pericardium 
to  it.  Large  quantity  of  dark,  partly  coagulated  blood  in  right  heart;  a  very  little 
in  the  left  heart. 

Stomach  empty,  lined  with  a  thin  layer  of  bile-stained  mucus.  In  the  lower.ileum 
several  patches  of  mucosa  of  a  dark  bluish  color,  each  about  6  inches  long.  Large 
intestine  filled  with  dry,  firm  feces.  In  the  upper  colon,  mucosa  ia  slate-colored, 
lower  down  normal  in  color. 

Liver  rather  firm,  surface  appears  slightly  roughened  and  mottled,  owing  to  conges- 
tion of  individual  lobules.  These  deeply  reddened  lobules  disseminated  through 
whole  parenchyma.  Hepatic  vessels  contain  much  thick  dark  blood. 

Kidneys  considerably  enlarged,  the  surface  besot  with  a  large  number  of  grayish, 
slightly  elevated  spots,  some  surrounded  by  a  dark-red  /one.  They  vary  from  one- 
half  to  one-fourth  inch  in  diameter  and  are  about  one-fourth  inch  apart.  On  sec- 
tion they  correspond  to  grayish  wedge-shaped  masses  extending  inward  through 
the  cortex  and  in  the  form  of  longitudinal  strije  through  the  pyramids  to  the  papillae 
These  infarcts  are  made  up,  examined  fresh,  chiefly  of  pus  corpuscles. 

Only  the  spleen  of  this  case  was  subjected  to  examination.  No  germs  were  seen  in 
cover-glass  preparations,  but  they  were  obtained  in  cultures. 

Sections  were  prepared  from  the  hepatized  lung  tissue  hardened  in  alcohol  and 
stained  with  alum-carmine  and  methylene  blue.  The  alveoli  were  found  completely 
occluded  with  cellular  masses  partaking  chiefly  of  the  character  of  leucocytes.  The 
red  blood  corpuscles  were  present  in  small  numbers.  Fibrin  not  detected.  The 
alveolar  capillaries  distended  with  red  corpuscles  projecting  into  the  lumen  of  the 
alveoli.  In  the  cell  masses  swine-plague  bacteria  are  very  abundant.  They  are 
scattered  between  the  cells,  not  in  clumps. 

Sections  from  the  kidney  hardened  in  alcohol  and  stained  with  methylene  blue 
showed  the  cellular  infiltration  in  the  cortex  and  extending  through  the  medullary 
portion  in  the  form  of  cylindrical  cell  masses  occupying  the  Inuieu  of  the  large  col- 
lecting tubules  which  are  completely  stripped  of  their  epitbelinm.  Swine-plague 
bacteria  are  disseminated  through  these  cell  masses  as  in  the  lung  tissue  already 
described. 

The  foregoing  notes  indicate  that  5  cubic  centimetres  of  a  peptone 
bouillon  culture  of  swine-plague  bacteria  injected  iuto  the  circulation  or 
the  lungs  may  be  fatal  within  24  hours.  They  also  show  a  tendency  to 
inflammation  of  the  large  serous  cavities,  especially  the  pleural,  even 
\\heii  the  injection  is  made  into  the  circulation.  This  inflammation  cor- 
responds closely  with  that  found  in  the  disease  as  it  occurs  in  nature. 


74 

Another  important  fact  is  the  production  of  pneumonia  not  only  when 
the  bacteria  are  injected  into  the  lungs,  but  when  introduced  into  the 
circulation. 

Feeding  and  subcutaneous  inoculation  failed  to  produce  disease. 
That  the  latter  will  now  and  then  produce  disease  is  well  shown  by  the 
following  case : 

Pig  No.  454  was  inoculated  February  28, 1891,  with  a  peptone  bouillon 
culture  of  the  swine-plague  germ  from  Case  15.  Three  cubic  centimetres 
were  injected  subcutaneously  into  each  thigh.  The  culture  was  one 
day  old,  prepared  from  an  agar  culture.  (Three  others  inoculated  at 
the  same  time  remained  well.)  The  pig  was  found  dead  March  2,  in  the 
early  morning.  It  had  thus  lived  between  36  and  48  hours  after  the 
inoculation. 

Black  and  red  female  pig,  weighing  about  50  pounds;  in  good  condition.  Consid- 
erable reddening  of  the  skin  of  ventral  aspect  ol  body  and  ears.  Subcutaneous  fat 
reddened.  From  the  cut  vessels  dark,  thick  blood  exudes.  Over  both  inoculated 
thighs  the  subcutaneous  vessels  are  extensively  injected,  forming  a  dense  network. 
The  subcutis  has  a  glistening  appearance.  On  the  right  thigh,  near  Poupart's  liga- 
ment, the  subcutaneous  connective  tissue  is  thickened,  yellowish  opaque,  and  friable, 
over  an  area  of  several  square  inches. 

On  opening  abdomen  the  intestines  appear  very  much  reddened.  A  few  elastic 
fibrils  stretched  across  coils  and  about  10  cubic  centimetres  of  turbid  serum  present. 

Stomach  contains  a  large  quantity  of  food,  Mucosa  not  affected.  Considerable 
catarrhal  inflammation  of  the  duodenum,  which  extends  into  jejunum.  The  hyperae- 
mia  extends  through  the  small  intestine,  but  much  less  intense.  Several  ascarides 
present.  The  mesenteric  glands  somewhat  congested;  in  two  of  them  old,  caseous 
masses,  occupying  nearly  the  entire  gland. 

Large  intestine  contains  a  large  quantity  of  semiliquid  feces.  Mucosa  normal. 
Meso-colic  glands  hypersemic. 

In  each  pleural  sac  about  10  cubic  centimetres  of  turbid  effusion.  Lungs  hyper- 
aemic  and  oadematous.  Interlobular  tissue  of  anterior  (or  cephalic)  lobes  slightly 
thickened  and  opaque,  the  result  of  some  former  inflammation.  In  trachea  and 
bronchi  some  reddish  frothy  liquid.  The  mucosa  shows  marked  injection  of  the 
minute  blood-vessels,  in  some  places  almost  hemorrhagic.  In  right  bronchus  a  small 
number  of  large  lung  worms. 

On  left  auricle  of  heart  ecchymoses.  In  left  ventricle  a  small  quantity  of  rather 
thick  dark  blood.  Right  ventricle  distended  with  it.  Coagulation  feeble. 

Liver  quite  pale  generally,  acini  distinctly  outlined.  Parenchymatons  inflaTnrna- 
tiou.  On  the  surface  may  be  seen  with  a  hand-lens  numerous  minute  grayish-yellow 
dots,  one  or  more  in  a  lobule  and  situated  chiefly  on  the  periphery.  In  sections  of 
fresh  tissue  they  appear  as  irregular,  opaque,  amorphous  patches.  In  stained  sections 
from  tissue  hardened  in  alcohol  they  appear  as  intralobular  aggregations  of  round 
cells  occupying  the  place  of  parenchyma  cells.  These  foci  are  probably  result  of 
some  former  disease.  In  the  intralobular  capillaries  occasional  masses  of  swine- 
plague  bacteria  detected.  (See  PI.  xi,  Fig.  4.) 

Spleen  enlarged  and  hyperatnic.  Kidneys  with  cortex  broadened.  The  base  of 
pyramids  somewhat  darker  red  than  normal. 

In  cover-glass  preparations  from  blood  and  spleen,  swine-plague  bacteria  present,  in 
the  blood  in  considerable  numbers. 

From  a  bit  of  spleen  pulp  two  agar  plates  prepared.  On  the  first,  after  24  hours, 
numerous  swine-plague  colonies  appeared  ;  on  the  second  nothing  developed. 

Agar  cultures  from  peritoneal  and  left  pleural  cavity  remained  clear. 


75 

An  agar  tube  inoculated  from  the  blood  contained  a  large  number  of  confluent 
colonies.  A  bouillon  tube  became  faintly  clouded.  Both  contained  only  swine-plague 
bacteria. 

An  agar  culture  from  the  liver  inoculated  with  platinum  wire  contained  on  the  fol- 
lowing day  a  considerable  number  of  swine-plague  colonies. 

Two  of  the  following  cases  are  of  importance  owing  to  the  peculiar 
lesions  of  the  joints  caused  by  the  inoculation. 

November  11.  With  a  peptone  bouillon  culture  of  swine-plague  bac- 
teria from  the  same  stock  culture  (Case  15)  the  following  inoculations 
were  made:  Nos.  405  and  408  received  into  a  vein  of  one  hind  leg  one- 
half  cubic  centimetre ;  Nos.  406  and  407  received  one- fourth  cubic  centi- 
metre. In  each  case  the  quantity  was  diluted  with  sterile  bouillon  so 
that  1  cubic  centimetre  of  liquid  was  injected. 

For  the  two  following  days  all  pigs  were  sick  and  refused  to  eat  the 
food  set  before  them.  Within  a  week  Nos.  406  and  408  had  nearly 
recovered,  No.  405  partially,  while  No.  407  was  unable  to  get  up  and 
continued  so  until  it  was  killed,  December  3,  by  a  blow  on  the  head. 
Its  chief  lesions  were  a  peculiar  necrotic  and  suppurative  condition  of 
the  joints  and  suppurative  pericarditis. 

Condition  of  animal  very  poor.  Enlargement  of  the  left  carpal  and  phalangeal 
joints,  of  the  right  elbow  joint,  and  both  hock  joints.  Along  the  inner  aspect  of  the 
left  scapula,  large  masses  of  yellowish  dry  pus  deposited  around  the  muscles.  Carpal 
joint  of  the  same  limb  much  enlarged.  On  opening  the  joint  a  considerable  quantity 
of  dry  pus  is  found  deposited  around  the  bones  and  between  the  tendons  over  the 
joint.  The  joint  surfaces  are  discolored,  the  cartilages  in  part  detached,  and  the 
small  bones  readily  crushed.  The  toes  enlarged,  the  enlargement  due  to  similar  snp- 
purative  changes  around  the  phalanges. 

Right  elbow  joint  enlarged;  joint  cartilages  greenish,  opaque.  Around  the  joint 
several  abscesses  containing  either  a  turbid  liquid  or  dry  cheesy  pus,  which  has  bur- 
rowed along  the  intermuscular  septa  of  the  forearm.  Carpal  and  metacarpal  joints 
of  this  limb  not  affected. 

On  both  hind  limbs  the  tarsal  and  metatarsal  joints  very  much  enlarged  and  in  the 
same  condition  as  those  just  described.  In  a  small  number  of  ribs  the  sternal  articu- 
lation involved  in  suppuration.  Over  the  lower  ribs  on  the  right  side  the  intermus- 
cular septa  are  imbedded  in  masses  of  dry  cheesy  pus. 

Within  the  lymphatic  glands  at  the  angle  of  the  jaw  and  in  the  inguinal  region  are 
minute  yellowish  masses. 

Lungs  normal.  Pericardium  thickened,  adherent  to  the  heart  surface  by  means  of 
a  layer  of  brittle,  straw-colored  pus,  covering  the  entire  heart  surface  with  exception 
of  a  small  area  on  the  left  ventricle,  to  which  the  pericardium  is  attached  by  means 
of  delicate  fibrous  tissue.  The  pus  is  most  abundant  at  the  base. 

The  digestive  tract  free  from  inflammatory  changes.  Stomach  contains  a  small 
quantity  of  liquid  of  a  deep  yellow  color,  and  some  mucus. 

Kidneys  show  on  the  surface  a  small  number  of  discolored,  slightly  depressed  spots, 
corresponding  to  pale,  whitish,  wedge-shaped  infarcts,  extending  into  medullary 
portion. 

Liver  discolored  in  spots  and  patches  on  the  surface.  These  also  seen  in  sections. 
Gall  bladder  contains  a  dark-greenish  solid  mass,  cutting  like  firm  cheese  and  filling 
up  the  entire  space  of  the  bladder. 

One  tarsal  joint  saved  and  opened  for  bacteriological  examination.  The  skin  is 
removed,  the  sac  of  the  abscess  thoroughly  scorched  and  opened  through  the  scorched 
area  with  a  flamed  knife.  A  considerable  quantity  of  greenish-yellow  liquid  holding 


76 

in  suspension  brittle  masses  of  pus  wells  out.  From  this  liquid  one  inclined  agar,  one 
bouillon  tube,  and  three  agar  plates  prepared.  The  agar  and  the  bouillon  tube  con- 
tained active  growths  of  the  injected  swine-plague  germ.  On  the  first  agar  plate 
an  immense  number  of  minute  colouies  appeared;  on  the  second  about  two  hundred, 
and  on  the  third  very  few.  From  these  plates  all  colonies  examined  were  made  up  of 
swine-plague  bacteria. 

A  rabbit  inoculated  subcutaneously  with  a  particle  of  the  pus  died  within  20  hours. 
In  cover-glass  preparations  from  liver  and  spleen,  and  in  an  agar  culture  from  the 
latter  organ,  swine-plague  germs  demonstrated. 

Another  case  of  suppurative  changes  in  the  joints  following  intra- 
venous inoculation  is  the  following: 

No.  411  received,  December  4,  1J  cubic  centimetres  bouillon  culture  of  swine- 
plague  bacteria  into  a  vein  of  one  hind  limb.  It  immediately  became  very  sick,  was 
unable  to  get  up,  and  died  December  22.  It  was  greatly  emaciated.  Both  carpal 
and  the  left  tarsal  joint  enlarged,  the  changes  within  the  joint  similar  to  those 
described  in  the  preceding  case.  Several  ribjoiutsin  the  same  condition.  In  this 
case  also  the  presence  of  the  virulent  swiue-^lague  bacteria  in  one  diseased  carpal 
joint  was  demonstrated  by  inoculating  two  rabbits  with  pus  therefrom.  Both  suc- 
cumbed within  20  hours  to  the  inoculation.  In  the  organs  the  characteristic  polar- 
stained  bacteria.  An  agar  and  a  peptone  bouillon  culture  from  the  spleen  of  the  pig 
remained  sterile. 

Two  other  pigs  inoculated  at  the  same  time  and  with  the  same  dose 
died  in  15  hours  with  commencing  peritonitis,  pleuritis,  and  pulmonary 
uedeimi.  In  both  the  stomach  was  hyperaemic. 

PATHOGENIC  EFFECT   ON  SMALLER   ANIMALS. 

The  great  virulence  of  the  swine-plague  bacteria  from  this  outbreak, 
as  compared  with  those  of  former  outbreaks,  is  even  better  shown  by 
the  inoculation  of  small  animals.  In  the  notes  given  below  it  will  be 
seen  that  not  only  rabbits  but  guinea-pigs  and  pigeons  succumb  to  very 
small  subcutaneous  doses  of  the  growth  from  cultures,  while  large 
fowls  are  killed  by  inoculations  into  the  muscular  tissue.  The  inocu- 
lation of  guinea-pigs  and  pigeons  with  cultures  from  previous  outbreaks 
was  usually  uncertain  even  though  rabbits  invariably  succumbed. 

Guinea-pigs. — October  2,  1890.  One  guiuea-pig  received  subcntaneously  into  the 
thigh  one-fourth  cubic  centimetre  of  a  peptone-bouillon  culture  of  swine-plague  bac- 
teria, a  second  one-twelfth  cubic  centimetre,  and  a  third  one  twenty-fourth  cubic 
centimetre.  The  liquid  in  each  case  was  diluted  with  2  parts  of  sterile  bouillon, 
hence  3  times  this  quantity  of  liquid  was  actually  injected. 

The  second  guinea-pig  died  within  24  hours.  At  the  point  of  inoculation  consider- 
able gelatinous  osderua,  the  blood  vessels  injected,  and  the  muscles  of  thigh  covered 
with  a  thin,  grayish  layer.  Stomach  and  small  intestine  hyperaemic.  Spleen  en- 
larged, dark  colored.  In  blood,  spleen,  and  liver  very  few  bacteria.  An  agar  culture 
from  the  spleen  developed  only  colonies  of  swine-plague  bacteria.  The  first  guinea- 
pig  died  several  hours  later  with  similar  lesions.  Peyer's  patches  hypertemic.  A  mod- 
erate number  of  swine-plague  bacteria  in  the  various  organs.  The  third  guinea-pig 
died  in  about  36  hours  with  the  same  lesions. 

October  7.  A  guinea-pig  was  inoculated  with  one  one-hundredth  cubic  centimetre 
of  a  peptone-bouillon  culture.  It  died  in  40  hours.  The  small  intestine  very  hyper- 
jemic,  occasional  patches  of  punctiform  hemorrhages  in  mncosa.  A  small  number  of 
bacteria  in  the  various  organs  not  showing  a  distinct  polar  stain. 


77 

October  14.  Two  guinea-pigs  were  inoculated,  one  with  one  one-thousandth  cubic 
centimetre  and  the  other  with  one  forty-thousandth  cubic  centimetre  of  a  peptone- 
bouillou  culture.  The  first  died  in  36  to  40  hours,  the  second  in  8  days.  In  this 
latter  case  there  was  considerable  purulent  thickening  of  the  snbcutis  arouud  the 
place  of  injection.  The  intestines,  liver,  and  spleen  covered  by  a  thin  layer  of  cellu- 
lar and  Hbrinous  exudate.  Very  few  bacteria  in  the  various  organs  and  the  exudate. 

Numerous  additional  iuoculatious  of  very  small  doses  into  guinea-pigs  confirmed 
the  fatal  effect  of  this  organism  on  this  species  of  animals. 

Mice. — November  15,  1690.  Two  gray  mice  inoculated  with  one  or  two  drops  of 
peptone-bouillon  culture  died  within  20  hours.  In  the  spleen  numerous  swine-plague 
bacteria  which  show  the  polar  stain  very  well  in  stained  preparations. 

Pigeons. — No.  1  inoculated  by  an  injection  of  0.3  cubic  centimetre  of  a  turbid  sus- 
pension from  an  agar  culture  24  hours  old.  The  injection  was  made  under  the  skin 
of  one  pectoral  muscle.  Pigeon  No.  2  inoculated  in  the  same  way  with  0.2  cubic 
centimetre,  the  needle  of  the  syringe  penetrating  superficially  the  pectoral  muscle. 

No.  2  died  next  morning.  Parboiled  appearance  of  inoculated  muscle.  Liver 
remarkably  pale  and  firm.  In  blood  and  liver  immense  numbers  of  bacteria  showing 
polar  stain  very  beautifully. 

No.  1  dies  in  24  hours.  Slight  subcutaneous  infiltration  at  point  of  inoculation. 
Liver  in  same  condition  as  in  No.  2.  Considerable  hyperaumia  of  mucosa  of  duode- 
num and  adjoining  small  intestine.  Contents  stained  reddish.  Bacteria  not  so  numer- 
ous as  in  preceding  case. 

These  inoculations  having  proved  successful,  two  pigeons  were  inocuiated  with  very 
small  doses  from  an  agar  culture  from  pigeon  No.  2,  three  days  old. 

No.  3.  Skin  over  pectoral  incised  with  a  lancet  and  a  loop  dipped  into  the  culture 
and  rubbed  into  subcutis. 

No.  4.     Skin  incised  and  a  minute  portion  on  platinum  wire  rubbed  into  subcutis. 

Both  dead  next  morning,  i.  e.,  within  18  hours.  Bacteria  abundant  as  in  preceding 
cases.  Livers  pale  and  firm. 

Foiolis. — Two  adult  hens,  inoculated  in  the  same  manner  as  pigeons  Nos.  3  and  4,  but 
with  a  slightly  increased  quantity  on  the  platinum  loop,  remained  unaffected. 

Two  other  adult  hens  were  inoculated  with  the  same  bacteria  from  an  agar  culture 
suspended  in  bouillon  until  turbid.  A  hypodermic  syringe  was  used  and  the  needle 
passed  superficially  into  the  fibers  of  the  pectoral  muscle.  One  fowl  received  one- 
fourth  cubic  centimetre,  the  other  one-half  cubic  centimetre.. 

The  first  died  in  24  hours.  No  local  reaction  perceptible.  The  liver  is  very  pale ; 
sprinkled  over  it  many  whitish  points,  character  not  determinable.  Intestines  nor- 
mal except  cjeca,  which  have  some  ecchymoses  under  serosa.  Large  number  of  bac- 
teria in  blood  and  liver  showing  polar  staining  very  well. 

The  second  fowl  died  in  36  hours.  Liver  very  pale  and  sprinkled  with  ecchymoses 
along  the  course  of  the  superficial  vessels.  In  liver  few,  in  blood  large  numbers  of 
the  injected  bacteria. 

TWO    BACILLI    ISOLATED    FROM    THIS    OUTBREAK    CLOSELY    RESEM- 
BLING HOG  CHOLERA  BACILLI. 

The  facts  thus  far  given  are  sufficient  to  prove  that  in  this  outbreak 
the  swiue- plague  bacteria  were  the  chief  if  not  the  only  cause  of  the 
epizootic.  In  the  course  of  the  investigations  two  kinds  of  bacteria 
were  obtained,  which  deserve  special  attention  owing  to  their  resem- 
blance to  hog-cholera  bacilli. 

Owing  to  preoccupation  of  the  writer  with  Texas  fever  investigations 
the  cultures  from  cases  13  to  J7,  inclusive,  were  made  largely  by  Dr.  V. 
A.  Moore,  assistant  in  the  laboratory,  and  he  was  directed  to  pay  special 


78 

attention  to  all  motile  bacteria  having  any  resemblance  to  hog-cholera 
bacilli.  Four  of  such  were  isolated,  one  from  the  lung  of  No.  14,  one 
from  the  spleen  of  No.  15.  one  from  the  spleen  of  No.  16,  and  one  from  the 
kidney  of  No.  385.  These  four  bacilli  the  writer  subjected  to  a  very  care- 
ful examination.  Those  from  Nos.  14  and  385  were  found  to  be  iden- 
tical with  the  common  intestinal  germ,  bacillus  coli  communis.  Those 
from  the  spleen  of  Nos.  15  and  16  grew  very  much  like  hog- cholera 
bacilli  on  gelatine  plates  and  in  rolls.  To  bring  out  the  differences  ob- 
served we  will  call  the  bacilli  from  Case  15  y  and  those  from  Case  16  6. 

In  gelatine  rolls  d  could  not  be  distinguished  from  a  parallel  roll  cul- 
ture of  virulent  hog-cholera  bacilli.  The  surface  colonies  of  y  presented 
a  somewhat  different  type,  in  that  they  spread  in  a  thinner  layer  with 
very  thin  edges,  somewhat  like  bacillus  coli.  They  differed,  however, 
from  colonies  of  the  latter  by  their  very  restricted  growth,  attaining  a 
diameter  of  only  1£  to  2  millimetres. 

Both  caused  considerable  turbidity  of  peptone  bouillon,  while  viru- 
lent hog-cholera  bacilli  cause  only  cloudiness,  which  very  rarely  merges 
into  a  moderate  turbidity.  These  bacilli  multiplied  therefore  far  more 
energetically  in  bouillon  than  do  virulent  hog-cholera  bacilli.  There 
were  other  slight  differences  between  these  two  bacilli.  Thus, 
while  y  caused  uniform  turbidity  of  the  culture  fluid,  d  grew  more  or 
less  in  clumps,  which  caused  a  rapid  settling  of  the  growth  in  spite  of 
the  inotility  of  the  bacilli.  When  the  culture  was  shaken  up  numerous 
clumps  and  flakes  rose  from  the  bottom.  In  the  hanging  drop  these 
bacilli  presented  a  strange  appearance.  The  various  clumps,  composed 
of  10  or  more  bacilli,  moved  rapidly  in  various  directions  across  the 
field  of  the  microscope.  This  peculiarity  of  6  maintained  itself  after 
passing  through  several  rabbits  and  many  cultures.  In  their  patho- 
genic power  these  two  bacilli  differed  not  only  from  hog-cholera  bacilli, 
as  they  are  usually  encountered  in  outbreaks,  but  from  one  another,  as 
the  following  experiments  show  : 

Bacillus  y.  Plate  cultures  made  from  original  culture  and  bouillon 
inoculated  from  a  colony.  When-  24  hours  old,  this  culture  was  used 
to  inoculate  2  rather  large  rabbits. 

One  white  rabbit  received  subcutaneously  0.3  cubic  centimetre  cul- 
ture liquid. 

One  black  rabbit  received  into  an  ear-vein  0.3  cubic  centimetre 
culture  liquid. 

Two  weeks  thereafter,  neither  having  shown  any  signs  of  disease, 
they  were  reinoculated.  The  black  one  received  1  cubic  centimetre, 
the  white  0.5  cubic  centimetre,  both  into  an  ear  vein. 

The  white  rabbit  remained  unaffected.  It  was  killed  after  16  days, 
but  no  lesions  were  found.  The  black  one  died  in  36  hours.  The  blood 
was  thick,  tarry;  the  left  lung  hypostatic;  the  spleen  small.  No 
bacteria  in  cover-glass  preparations  from  the  spleen.  This  result  did  not 
place  these  bacilli  above  the  level  of  the  ordinary  intestinal  bacteria 


79 

(bacillus  coli) ;  for  1  cubic  centimetre  of  the  latter  produces  death  in 
rabbits  with  equal  promptness  when  injected  into  an  ear  vein.  Two 
additional  intravenous  inoculations  were  made  April  28: 

One  rabbit,  weighing  about  3  pounds,  0.3  cubic  centimetre  bouillon 
culture. 

Two  rabbits,  weighing  about  4  pounds,  0.6  cubic  centimetre  bouillon 
culture. 

Both  rabbits  remained  apparently  unaffected. 

Finally,  on  May  21,  two  rabbits,  weighing  each  3  pounds,  were  inocu- 
lated by  receiving  into  an  ear  vein  0.6  cubic  centimetre  of  a  bouillon 
culture.  The  agar  culture  had  been  replated,  and  from  a  colony  this 
bouillon  culture  was  prepared.  Neither  rabbit  showed  signs  of  disease. 

It  did  not  seem  worth  while  to  spend  any  more  time  on  this  obviously 
non-pathogenic  organism.  Its  marked  resemblance  in  morphological 
and  biological  characters  to  the  hog-cholera  bacillus  makes  it  highly 
probable  that  it  is  closely  related  to  this  latter  germ. 

Bacillus  3.  Similar  experiments  with  this  bacillus  from  case  16 
proved  that  this  one  did  possess  pathogenic  properties,  though  feeble 
in  character. 

From  the  original  culture  a  gelatine  plate  was  prepared  and  a  pep- 
tone bouillon  tube  inoculated  from  a  colony.  When  4  days  old  two 
small  yellow  rabbits  were  inoculated.  One  received  about  0.4  cubic 
centimetre  under  the  skin,  the  other  the  same  quantity  into  the  ear 
vein.  The  latter  rabbit  died  in  6  days. 

The  spleen  is  very  large,  dark,  and  softened,  and  contains  a  large  number  of 
what  appear  to  be  hog-cholera  bacilli.  The  liver  shows  areas  of  necrosis.  The  gall- 
bladder attached  by  inflammatory  exudation  to  the  omentum.  The  lungs  oedematous. 
Fatty  degeneration  of  cortex  of  kidneys.  The  small  intestine  filled  with  a  glairy 
yellowish  liquid.  The  cultures  from  this  case  contained  only  the  injected  bacilli, 
exhibiting  in  bouillon  tubes  the  peculiar  characters  described  above. 

The  rabbit  which  received  the  subcutaneous  dose  remained  apparently  unaffected. 
After  22  days  it  was  inoculated  with  swine  plague  and  found  dead  the  following 
morning.  At  the  place  of  the  first  inoculation  a  cyst  nearly  1  inch  in  diameter  con- 
taining curdy  pus.  la  the  appendix  veriniforinis  from  twenty  to  thirty  whitish  nod- 
ules under  serosa.  Similar  nodules  on  Peyer's  patch  near  ileo-caecal  valve. 

A  rabbit  which  received  an  injection  of  0.3  cubic  centimetre  into  abdo- 
men remained  well.  When  killed,  10  days  after  the  inoculation,  the  same 
appearances  of  appendix  of  caecum  were  found  as  those  just  described. 

Several  weeks  later,  with  the  culture  obtained  from  the  first  rabbit, 
four  rabbits  were  inoculated,  each  by  an  injection  into  an  ear  vein  of  0.2 
cubic  centimetre.  These  all  died  within  36  to  48  hours.  In  the  one 
which  lived  48  hours  the  following  lesions  were  observed  : 

Large,  dark  spleen.  Interlobular  network  of  a  yellowish  color  through  the  whole 
liver.  Under  the  microscope  this  appeared  as  fatty  degeneration  of  the  periphery  of 
the  acini.  Lungs  oedematous.  Left  ventricle  of  heart  in  advanced  fatty  degeneration. 
Cloudy  swelling  of  kidneys.  In  the  spleen  large  numberb  of  bacilli  which  appear 
somewhat  larger  than  hog-cholera  bacilli  and  are  usually  in  pairs.  Cultures  from 
this  case  contain  only  the  injected  bacilli. 


80 

That  the  bacillus  6  is  an  attenuated  variety  of  the  hog-cholera  ba- 
cillus can  not  be  doubted  when  these  rabbit  inoculations  are  taken  into 
consideration.  There  was,  moreover,  a  gradual  increase  in  virulence 
observed  from  one  inoculation  to  the  subsequent  one.  Thus  the  first 
rabbit,  which  was  a  small  one,  received  0.4  cubic  centimetre  bouillon  cul- 
ture into  a  vein,  and  lived  6  days.  The  second  rabbit  received  0.2  cubic 
centimetre,  and  died  in  2  days.  Subsequent  inoculations  showed  that 
.05  cubic  centimetre  was  fatal  in  a  few  days,  while  smaller  quantities 
caused  a  disease  from  which  the  rabbits  recovered. 

We  have  thus  seen  that  in  addition  to  the  swine-plague  bacteria, 
which  produced  disease  both  after  inoculation  and  exposure  to  diseased 
swine,  two  motile  bacteria  were  isolated  from  cases  15  and  16,  but  from 
no  other.  These  both  resembled  hog-cholera  bacilli  very  closely,  and 
undoubtedly  are  related  to  them.  But  they  differed  from  each  other  in 
several  particulars,  notably  in  virulence.  While  the  one  from  No.  16 
was  shown  to  be  an  undoubted  but  very  attenuated  variety  of  hog- 
cholera  bacilli,  the  one  from  No.  15,  though  it  may  also  be  an  attenu- 
ated variety,  has  so  little  virulence  that  its  bearing  upon  the  outbreak 
in  question  must  be  regarded  as  entirely  negative.  As  to  the  other 
bacillus  the  question  is  not  so  simple.  It  may  be  seriously  doubted 
whether  it  had  anything  to  do  in  producing  the  disease,  since  its  pres- 
ence was  detected  in  but  one  out  of  eleven  cases,  and  since  hog-cholera 
bacilli  from  genuine  hog-cholera  outbreaks  appear  quite  regularly  in 
cultures  from  the  spleen.  Moreover,  the  virulence  of  the  latter  is  many 
times  greater  than  that  of  the  bacilli  in  question.  Thus,  to  test  this 
matter  thoroughly,  one  pig  received  into  the  lungs  5  cubic  centimetres 
of  a  bouillon  culture,  another  5  cubic  centimetres  into  the  abdomen, 
and  several  others  7  cubic  centimetres  each  directly  into  the  blood. 
None  of  them  showed  any  signs  of  illness  after  such  treatment.  Lastly, 
two  pigs  were  fed,  after  a  fast  of  24  hours,  with200  cubic  centimetres  of 
a  bouillon  culture  each.  This  feeding  was  repeated  on  two  successive 
days.  A  slight  diarrhea,  lasting  a  few  days,  was  the  only  visible  effect. 

On  the  other  hand  it  is  not  to  be  denied  that  these  bacilli  may  have 
occasioned  a  part  at  least  of  the  intestinal  disease  observed  in  this  out- 
break. The  truth  may  be  that  these  attenuated  hog-cholera  bacilli, 
brought  from  distant  outbreaks  by  individual  animals  which  have  sur- 
vived such  outbreaks  or  proved  themselves  insusceptible  at  the  time, 
had  no  effect  on  the  animals  brought  in  contact  with  them  until  the 
swine  plague  broke  out,  when  they  may  have  started  into  activity  and 
contributed  to  the  fatality  of  the  disease.  That  the  bacillus  6  from 
case  16  should  have  been  the  cause  of  the  outbreak  and  the  swine  plague 
bacteria  secondary  to  it  would  seem  very  far-fetched  in  the  light  fur- 
nished by  the  experiments  with  the  swine-plague  bacteria. 

In  addition  to  the  attenuated  hog  cholera  bacilli,  another  disease 
germ  was  isolated  from  cultures  prepared  on  the  farm  from  some  of  the 
earlier  cases.  This  germ  is  briefly  referred  to  in  the  autopsy  notes  as 
a  rather  large  bacillus,  which  multiplied  in  the  condensation  water  of 


81 


agar  cultures  but  not  on  the  surface.  It  produces  spores  which  are 
formed  in  the  central  portions  of  the  rod.  The  latter  during  the  de- 
velopment of  the  spore  becomes  spindle-shaped.  This  bacillus  does  not 
multiply  in  culture  tubes  under  ordinary  conditions,  but  requires  media 
more  or  less  free  from  oxygen.  It  belongs  to  the  group  of  anaerobic 
bacteria,  and  is  probably  identical  with  the  bacillus  of  malignant  O3dema. 
Whether  it  is  the  bacillus  which  I  have  frequently  detected  in  swine 
and  called  "  post-mortem"  bacillus  it  is  impossible  to  state,  since  I  have 
made  no  special  effort  to  cultivate  the  latter  aud  test  its  virulence  on 
animals. 

The  bacillus  in  question  grows  in  deep  layers  of  agar  in  test  tubes. 
The  isolated  colonies  develop  quite  slowly  and  after  1  or  2  weeks  attain 
a  maximum  diameter  of  2  millimetres.  The  surface  of  the  fully  devel- 
oped spherical  colony  is  closely  beset  with  radiating  finger-like  projec- 
tions, which  are  perhaps  one-fourth  as  long  as  the  diameter  of  the  entire 
colony.  An  addition  of  glucose  to  the  agar  favors  the  growth  of  the 
bacilli  and  causes  the  prod  action  of  considerable  gas,  which  may  break 
up  the  agar  column  and  force  portions  nearly  out  of  the  tube.  This 
bacillus  also  multiplies  in  peptone  bouillon  containing,  say,  2  per  cent, 
of  glucose,  provided  oxygen  is  absent.  For  this  purpose  the  fermenta- 
tion tube,  which  I  have  found  very  useful  in  bacteriological  work,  is  very 
well  adapted.*  When  such  tubes  are  inoculated  a  faint  cloudiness  of 

*  The  fermentation  tube  has  been  iu  use  for  many  years  in  various  kinds  of  biologi- 
cal work.  Its  value  in  bacteriological  work  as  a  culture  tube  I  have  already  called 
attention  to  (Centralblatt  f.  Bakterioloyie  (1890)  vn,  p.  502),  but  reproduce  here  a  few 

suggestions  as  to  its  use.  The  tube,  reduced 
one-half,  is  shown  in  the  accompanying  cut. 
After  it  has  been  plugged  with  cotton  wool 
and  sterilized  in  the  dry  hot  air  oven  it  is  filled 
with  the  culture  liquid  and  steamed  on  three 
successive  days.  The  air  collecting  at  the  top 
near  b,  which  has  been  forced  out  of  the  liquid, 
should  be  removed  immediately  after  each 
steaming  by  gently  tilting  the  tube.  After 
the  third  steaming,  the  liquid  in.  b  is  entirely 
freed  of  dissolved  air.  The  tube  is  inoculated 
with  platiuuni  wire,  loop,  or  pipette  as  are  or- 
dinary tubes.  A  large  number  of  bacteria, 
especially  those  living  in  the  intestines  of  an- 
imals, are  capable  of  setting  up  a  fermentation 
when  glucose  and  other  sugars  are  present. 
The  gas  collecting  at  the  top  in  b  is  composed 
chiefly  of  COa  and  H. 

I  have  found  the  fermentation  tube  very  val- 
uable in  the  diagnosis  of  hog-cholera  bacilli, 
which  are  capable  of  fermenting  glucose,  etc. 
Hog-cholera  bacilli  from  a  large  number  of  out- 
breaks tested  thus  far  all  manifest  this  phenom- 
enon, and  it  may  be  safe  to  assert  that  any 
bacilli  resembling  hog  cholera  which  do  not 
produce  gas  are  not  hog-cholera  bacilli. 

1614 6 


82 

the  liquid  appears  within  1  or  2  (lays,  and  gas  bubbles  rise  iu  the  closed 
branch.  After  a  few  more  days  the  liquid  in  the  closed  branch  is  in 
part  replaced  by  gas,  which  continues  to  form  for  a  week  or  longer. 
Meanwhile  the  bacilli  have  become  deposited  in  the  bottom  of  the  tube 
as  a  whitish,  flocculent  mass.  By  cultivation  in  this  way  I  was  able  to 
keep  these  bacilli  alive  for  many  months  until  opportunity  offered  to 
test  them  on  animals.  That  they  are  pathogenic  and  may  cause  ma- 
lignant cedema  the  following  inoculations  are  sufficient  to  demonstrate : 

May  22,  1891,  3  p.  in.  From  a  culture  iu  a  fermentation  tube  14  days  old  one-  half 
cubic  centimetre  of  the  turbid  deposit  withdrawn  and  injected  under  the  skin  of  a 
rather  large  guinea-pig  in  the  region  of  the  abdomen. 

The  animal,  apparently  well  at  9  a.  m.  next  morning,  lay  down  at  10  a.  in.,  and  died 
at  1  p.  in.  On  examination  very  extensive  sanguinolent  osdema  of  the  subcutis  over 
abdomen  and  part  of  thorax.  On  left  thigh  the  oedema  accompanied  with  much  dis- 
tension of  the  subcutis  with  gas.  The  serosa  of  abdominal  cavity  discolored  and 
vessels  injected.  Both  sides  of  heart  contain  dark  soft  clots.  In  the  blood-stained 
subcutis  large  numbers  of  the  injected  bacilli,  in  the  spleen  a  few,  in  the  blood  none 
observed.  Two  fermentation  tubes  were  inoculated  with  blood  and  a  particle  of 
spleen  pulp,  respectively.  In  both  a  typical  growth  appeared  in  a  few  days. 

At  the  same  time  a  colony  of  these  bacilli  was  removed  from  a  glucose  agar  tube, 
now  22  days  old,  and  placed  into  the  subcutis  of  abdomen  of  another  guinea-pig 
through  an  incision.  No  symptoms  observed  until  48  hours,  when  the  animal  rested 
with  abdomen  on  floor  of  cage  and  did  not  stir  when  aroused.  Apparently  neither 
drowsy  nor  iu  pain.  It  was  found  dead  on  the  morning  of  the  third  day  (GO  hours). 
The  lesions  as  well  as  the  distribution  of  the  bacilli  and  cultures  from  blood  and 
spleen  were  the  same  as  in  preceding  case. 

A  pig  inoculated  subcutaneously  with  2  cubic  centimetres  of  turbid  deposit  from  a 
fermentation  tube  showed  no  signs  of  disease. 

Whether  these  bacilli  can  be  implicated  in  the  death  of  some  cases  of 
this  outbreak  in  which  swine-plague  bacilli  were  not  detected,  these 
inoculations  will  not  permit  us  to  decide.  The  bacilli  at  the  date  of 
inoculation  had  been  cultivated  for  10  months,  and  hence  may  have 
become  attenuated  in  the  meantime. 

X. 

At  the  end  of  1890,  Veterinarian  E.  C.  Schroeder  was  directed  by  the 
chief  of  the  Bureau  to  make  some  examinations  of  swine  diseases  in 
the  West  with  the  object  of  still  further  determining  the  distribution  of 
hog  cholera  and  swine  plague. 

Among  the  several  herds  examined  only  one  deserves  mention,  be- 
cause positive  bacteriological  results  were  obtained.  This  herd  was 
found  about  1£  miles  south  of  Chillicothe,  Missouri,  where  greater  or 
smaller  losses  from  infectious  swine  diseases  are  said  to  occur  each 
year. 

Cultures  were  made  by  Dr.  Schroed  er  on  agar,  and  these  were  care 
fully  examined  by  the  writer  subsequently.  The  cultures  from  one 
animal  contained  only  swine-plague  bacteria,  those  from  another  only 
hog-cholera  bacilli.  This  outcome  again  illustrates  the  caution  which 


83 

must  be  exercised  iu  isolating  the  bacteria  obtained  from  diseased  ani- 
mals, so  that  the  characters  of  two  different  bacteria  may  not  be 
confounded  and  regarded  as  one,  as  has  probably  been  done  by  Bill- 
ings in  his  investigations.  No  conclusions  are  drawn  from  the  meager 
details  below  as  to  which  bacteria  may  have  been  the  predominating 
cause  of  the  disease.  They  simply  illustrate  the  wide  diffusion  and  in- 
termingling of  two  pathogenic  bacteria. 

The  following  brief  synopsis  has  been  condensed  from  Dr.  Schroeder's 
notes  of  the  post-mortem  examination : 

No.  1.  December  27,  1890.  Dead  several  days.  Animal  had  been  opened  by  owner. 
Spleen  greatly  congested.  Intestines  could  not  be  examined.  Right  lung  almost 
completely  hepatized.  Epicarditis.  Lymph  glands  in  general  much  congested. 

No.  2.  January  2,  1891.  Several  foci  of  hepati nation  in  lungs.  Muco-purulent  con- 
dition of  smaller  air  tubes.  Spleen  very  large,  dark,  softened.  Petechise  in  cortical 
portion  of  kidneys.  Mnch  mucus  in  stomach.  Feces  in  large  intestine  very  dry, 
coated  with  mucus.  Patches  of  hypersemia ;  no  ulceration. 

No.  3.  January  3.  On  pubic  region  a  large  open  wound,  with  subjacent  tissue  very 
much  thickened  by  inflammatory  deposits.  Spleen  very  large,  dark,  and  friable. 
Slight  exudative  peritonitis.  Congestion  of  fundus  of  stomach.  Feces  in  large 
intestine  exceedingly  dry  and  covered  with  mucus.  Several  inches  below  valve  a 
blackish,  necrotic  patch,  1^  inches  long  and  a  half-inch  wide  (Peyer's  patch  I).  Mucosa 
congested  in  isolated  patches.  No  other  ulceration  observed.  Lungs  hyperainic. 
No  hepati/ation.  Hemorrhagic  condition  of  auricles  of  heart.  Petechiae  on  epicar- 
tliuin  of  ventricles. 

No.  4.  January  3.  Black  female,  killed  by  a  blow  on  head.  Spleen  as  in  No.  3.  Di- 
gestive tract  normal,  with  exception  of  patches  of  congestion  in  large  intestine  and 
what  appear  to  be  two  small  ulcers  on  ileo-caecal  valve  (enlarged  mouths  of  glands  ?)• 
Slight  exudative  peritonitis.  Lungs  free  from  hepatization. 

Bacteriological  examination.  From  No.  1  no  cultures  made,  owing  to  post-mortem 
changes. 

From  No.  2  bits  of  the  spleen  placed  in  two  agar  tubes.  On  January  19  there  were 
about  100  isolated  and  confluent  colonies  on  the  agar  surface  in  one  of  the  tubes.  In 
the  other  no  growth  had  appeared.  These  colonies  were  carefully  examined  and 
found  to  be  swine-plague  bacteria.  Many  of  the  colonies  were  dead,  as  the  agar  had 
dried  out  somewhat.  Transferred  to  bouillon  and  other  media,  the  diagnosis  was 
confirmed.  These  bacteria  were,  however,  more  or  less  attenuated  as  regards  patho- 
genic effect. 

January  31.  Two  white  rabbits  of  medium  size  inoculated,  one  subcutaneously  on 
one  ear  with  a  loop  dipped  into  condensation  water  of  an  agai  culture,  the  other  under 
skin  of  abdomen  in  same  manner.  Both  rabbits  were  very  quiet  for  several  days,  the 
former  with  ear  drooping  and  very  much  reddened.  On  the  eleventh  day  it  was 
chloroformed.  The  greater  part  of  the  inoculated  ear  blackish  ;  hard,  like  a  board ; 
necrosed.  A  purulent  inflammation  extending  from  ear  down  on  the  face  and  neck. 
Heart  muscle  pale  and  flabby.  Much  fat  in  the  fibers.  Fatty  degeneration  of  con- 
voluted tubes  in  cortex  of  kidneys.  Numerous  granular  casts  in  urine.  Spleen  small 
and  pale.  Fatty  condition  of  liver. 

The  second  rabbit  was  well  at  this  time.  When  killed  a  small  abscess  in  subcutis, 
with  ecchymosis  of  contiguous  abdominal  muscles.  No  internal  lesions. 

From  No.  3  agar  cultures  had  been  made  from  spleen  and  liver.  Both  developed, 
and  evidently  contained  the  same  bacteria.  The  liver  culture  contained  a  consider- 
able number  of  isolated  colonies.  From  these  gelatin  plates  were  made.  The  vari- 
ous culture  tests  and  the  microscopic  characters  (size,  motility,  etc.),  all  pointed  to 
hog-cholera  bacilli.  The  diagnosis  was  confirmed  by  the  following  inoculations; 


84 

One  rabbit  received  into  an  ear  vein  one-fifth  cubic  centimeter  bouillon  culture 
derived  from  a  colony  on  a  gelatine  plate.  One  rabbit  received  same  dose  of  same 
culture  under  skin  of  flank. 

The  first  rabbit  died  within  48  hours.  No  local  lesion.  Spleen  very  large,  dark, 
and  firm.  Liver  fatty.  Lungs  slightly  osdematous.  In  the  spleen  numerous  bacteria, 
resembling  hog-cholera  bacilli  in  every  way.  Cultures  confirmatory. 

The  second  rabbit  died  in  5  days.  At  the  place  of  iuoculation  purulent  infiltration 
of  skin  and  subcutis  with  ecchymoses  on  periphery.  Spleen  large,  dark,  firm.  Heart 
muscle  fatty.  Lungs  osdematous  and  hyperaemic  along  ventral  border.  In  liver 
interlobular  tissue  broadened,  pale,  representing  degeneration  of  periphery  of  acini. 
Cultures  contain  only  hog  cholera  bacilli. 

From  pig  No.  4  an  agar  culture  irom  the  spleen  failed  to  develop. 

XI. 

An  intermingling  of  hog  cholera  and  swine  plague  was  also  observed 
in  two  outbreaks  studied  in  1889,  and  very  briefly  referred  to  in  the  re- 
port of  the  Secretary  of  Agriculture  for  the  same  year  (p.  75).  These 
outbreaks  are  of  importance,  in  so  far  as  the  hog-cholera  bacilli  obtained 
therefrom  were  somewhat  modified  with  reference  to  their  biological 
and  pathogenic  properties.  It  was  evident  also  that  these  hog-cholera 
bacilli  were  the  predominating  cause  of  the  disease  in  many  of  the  ani- 
mals exposed,  and  the  full  report  is  therefore  reserved  for  another  pub- 
lication. The  investigations  are  here  mentioned  to  illustrate  once  again 
the  wide  distribution  and  frequent  intermingling  of  these  two  patho- 
genic bacteria. 


THE  BACTERIA  OF  SWINE  PLAGUE. 


MORPHOLOGICAL,  AND   BIOLOGICAL   CHARACTERS. 

If  a  cover-glass  preparation  from  the  spleen  pulp  of  a  rabbit,  which 
has  succumbed  16  to  20  hours  after  inoculation,  be  stained  in  alkaline 
methylene  blue  for  a  few  minutes,  and  examined  with  a  high  power 
either  in  water  or  after  it  has  been  permanently  mounted  in  balsam, 
a  very  large  number  of  swine-plague  bacteria  will  usually  be  found 
among  the  cells  of  the  spleen  pulp. 

These  bacteria  at  first  give  the  impression  of  very  minute  flattened 
cocci  in  pairs,  the  individuals  of  each  pair  separated  from  each  other 
by  a  small  intervening  space.  (See  Plate  xi,  Fig.  1.)  A  closer  inspection, 
however,  shows  that  each  pair  is  in  reality  a  single  elongated  body  of 
which  the  two  cocci  are  the  stained  extremities.  The  intervening  space 
is  the  unstained  connecting  body,  .the  borders  of  which  are  contin- 
uous with  those  of  the  stained  extremities  as  indicated  in  the  figure. 

The  two  end  pieces  have  usually  a  lunar  shape,  the  concavities  turned 
toward  each  other.  The  depth  of  the  concavity  varies  somewhat  and 
may  even  be  replaced  by  a  straight  line,  in  which  case  the  end  pieces 
have  a  hemispherical  shape. 

It  is  highly  probable  that  the  bacteria  as  described  above  are  in  a 
state  of  division,  the  two  stained  extremities  representing  the  two  future 
cells,  and  the  intervening  space  perhaps  a  common  membrane  without 
any  contents.  During  this  process  the  protoplasm  retracts  from  the 
central  portion  of  the  rod  and  gathers  at  the  two  extremities. 

In  stained  cover-glass  preparations  these  bacteria  are  not  infre- 
quently found  varying  in  length.  This  variation  is  mainly  due  to  the 
variation  in  length  of  the  middle  unstained  piece.  Thus  preparations 
of  the  same  germ  from  some  rabbits  may  show  a  very  short  middle  piece 
so  that  the  two  concave  borders  of  the  comparatively  large  end  pieces 
appear  to  touch  each  other  on  the  lateral  margins  of  the  bacterium.  In 
other  preparations  this  middle  piece  may  be  from  two  to  three  times  the 
size  of  each  end  piece.  In  a  preparation  from  the  spleen  of  a  rabbit 
inoculated  with  the  German  swine  plague  the  middle  piece  was  in  many 
bacteria  so  long  as  to  suggest  involution  or  degenerate  forms.  It  made 
the  entire  rod  one  and  one-half  to  two  times  longer  than  the  normal 
forms.  In  some  of  these  bacteria  one  end  piece  had  divided  and  the 
double  germ  resulting  therefrom  appeared  like  a  long,  feebly  stained 

85 


86 

bacillus,  in  which  there  were  in  both  ends  and  in  the  middle  of  the  rod 
the  deeply  stained  round  coccus-like  bodies.  In  all  the  variations  the 
stained  extremities  do  not  vary  much  in  size.  This  is,  therefore,  an  ad- 
ditional reason  why  these  extremities  should  be  regarded  as  daughter 
cells  in  process  of  separation  from  one  another. 

The  foregoing  description  applies  to  bacteria  taken  directly  from  the 
dead  animal  and  dried  on  cover  glasses.  In  this  dried  condition  after 
they  have  been  stained  and  mounted  in  balsam  they  are  about  1  /t* 
long  and  0.5  to  0.6  p  wide.  Their  ends  are  rounded  oft'  and  in  general 
their  form  is  that  of  a  somewhat  elongated  oval.  Besides  these  aver- 
age forms  there  may  be  others,  1.8  p  long  and  0.7  to  0.8  /*  broad.  Di- 
mensions larger  than  these  generally  belong  to  forms  evidently  abnormal 
in  development.  In  these  the  width  generally  remains  the  same  as  that 
of  the  shorter  forms. 

While  these  bacteria  in  cover-glass  preparations  from  pigs,  inoculated 
rabbits,  etc.,  are  the  same  in  appearance,  the  same  bacteria  in  sections 
of  tissues  hardened  in  alcohol  and  stained  in  the  same  way  do  not  cor- 
respond to  the  description  just  given.  They  are  smaller  than  the 
smallest  forms  described  above,  and  as  a  rule  do  not  show  distinctly 
the  unstained  middle  piece.  They  appear  under  high  powers  as  mi- 
nute uniformly  stained  oval  bodies.  It  is  evident  that  in  the  one  case 
the  drying  process  has  a  tendency  to  flatten  objects  out  against  the 
cover  glass,  while  in  the  hardening  process  there  is  a  tendency  to 
shrinking,  which  is  not  counteracted  in  any  way.  Hence  the  different 
appearance  may  be  due  simply  to  the  difference  in  the  mode  of  prep- 
aration. 

The  foregoing  description  applies  to  virulent  varieties  which  cause 
death  of  the  inoculated  rabbit  in  16  to  20  hours.  In  the  various 
organs  and  the  blood  the  inoculated  bacteria  are  present  in  large  num- 
bers. The  more  attenuated  varieties  do  not  produce  death  thus  quickly. 
The  rabbit  dies  in  from  3  to  10  days.  The  bacteria  have  meanwhile 
become  localized  in  the  peritoneal  cavity  or  the  pleural  cavity,  and 
produced  an  inflammatory  exudate  which  contains  immense  numbers  ot 
bacteria.  These  do  not  stain  so  well  as  those  described,  and  rarely 
show  the  polar  arrangement  of  the  protoplasm  distinctly.  There  is 
reason  to  suppose  that  many  of  these  forms  are  already  destroyed  by 
the  inflammatory  process. 

In  cultures  the  swine-plague  bacteria  are  smaller  than  in  the  bodies 
of  inoculated  animals.  Examined  in  water  they  appear  so  minute  that 
it  is  with  difficulty  that  they  are  detected  at  all  (Zeiss  apochr.  2  milli- 
metres, compens.  oc.  4).  In  general  they  answer  well  to  the  descrip- 
tion of  micrococci,  although  they  are  not  round  but  oval  in  form.  On 
the  border  of  the  drop  holding  them  in  suspension  the  polar  arrange- 
ment of  the  protoplasm  is  occasionally  detected. 

Swine-plague  bacteria  are    non-motile.    This  important  character 

*  Micromilliinetre  or  about  one  twenty-five  thousandth  of  an  inch. 


87 

serves  to  distinguish  them  at  ouce  from  hog-cholera  bacilli.  In  liquids 
an  active  Brownian  motion  is  frequently  seen  which  is  so  violent  at 
times  as  to  give  the  impression  of  spontaneous  motion.  They  do  not 
change  their  place,  however,  and  this  agitation  is  thus  readily  distin- 
guished from  the  very  active  flagellar  movemeut  of  hog-cholera  bacilli. 
Again,  flagella  are  easily  demonstrated  on  the  latter.  Dr.  V.  A.  Moore 
has  devoted  much  time  in  the  laboratory  to  bring  out  flagella  on  swiue- 
plagne  bacteria  without  success.  This  was  of  course  to  be  expected. 
No  spores  have  been  observed  in  any  of  the  conditions  under  which 
they  have  been  cultivated.  They  are  destroyed  in  liquids  by  a  tem- 
perature of  58°  C.  (136.4°  F.)  in  7  minutes.  Their  rapid  destruction 
by  drying,  disinfectants,  etc.,  renders  it  highly  probable  that  no  spores 
are  produced. 

The  question  whether  swine-plague  bacteria  should  be  called  bacilli 
or  micrococci  is  not  an  easy  one  to  settle  satisfactorily.  In  the  tissues 
and  very  rarely  in  cultures  they  may  appear  as  elongated  rods,  but  only 
under  abnormal  conditions.  Their  usual  form,  both  in  cultures  and  in 
sections  from  tissues,  is  that  of  an  oval,  the  longer  diameter  exceeding 
but  slightly  the  shorter  diameter.  While  we  are  inclined  to  call  them 
micrococci  as  least  misleading,  usage  seems  to  have  followed  the  Koch 
school  in  calling  them  bacilli.  In  the  present  report  they  are  simply 
denominated  bacteria,  and  the  matter  of  nomenclature  is  left  open. 

Swine-plague  bacteria  are  not  so  easily  cultivated  as  hog-cholera 
bacilli.  Besides  refusing  to  multiply  on  certain  media  in  which  hog- 
cholera  bacilli  readily  grow,  their  life  in  cultures  is  much  shorter. 
In  the  following  the  chief  characters  of  these  bacteria  in  the  various 
culture  media  are  given  somewhat  in  detail,  since  no  one  character 
is  sufficiently  peculiar,  and  all  are  necessary  to  positively  recognize 
the  species. 

The  growth  on  nutrient  gelatine  is  variable  and  therefore  not  reliable. 
The  bacteria  from  outbreaks  VII,  VIII,  and  IX,  as  a  rule,  refused  to 
multiply  in  gelatine.  Occasionally  colonies  develop  in  roll  cultures,  but 
the  growth  is  very  feeble  and  retarded,  and  may  be  overlooked  unless 
they  are  carefully  watched  for  longer  than  a  week.  An  increase  of 
alkali  seems  to  favor  their  growth. 

If  we  turn  to  the  bacteria  discovered  in  1886  and  1887  perhaps  the 
only  biological  difference  observable  is  the  more  abundant  growth  of 
these  varieties  in  nutrient  gelatine.  The  deep  colonies  were  from  one- 
fourth  to  one-half  millimetre  in  diameter;  the  surface  colonies  were  4  or 
5  times  as  large.  The  former  appeared  after  some  days  with  a  pale  mar- 
gin, the  central  portion  being  brownish,  granular.*  The  failure  to  grow 
on  gelatine  can  not  be  regarded  as  entirely  due  to  the  lower  tempera- 
ture in  which  gelatine  must  be  kept.  It  seems  partly  due  to  the  nature 
of  the  medium,  partly  to  the  adaptability  of  the  bacteria  to  be  cultivated. 

*  See  p.  89  and  Plate  iv  in  the  report  of  the  Bureau  of  Animal  Industry  for  1880, 
and  Plate  xu,  Fig.  3,  of  thia  report. 


88 

The  same  method  being  employed  in  the  preparation  of  gelatine  and 
agar,  the  fact  that  swine-plague  bacteria  will  develop  in  an  agar  tube 
when  a  gelatine  tube  by  its  side  inoculated  in  precisely  the  same 
manner  fails  to  develop  shows  that  some  physical  or  chemical  con- 
dition of  the  gelatine  is  at  fault.  The  gelatine  must  be  regarded  as  a 
drier  medium  than  the  agar,  which  dryness  is  not  so  favorable.  An- 
other possible  explanation  of  the  refusal  of  the  more  recently  cultivated 
varieties  to  multiply  in  gelatine  may  be  due  in  part  to  slight  improve- 
ments and  modifications  in  the  preparation  of  nutrient  gelatine  and 
agar.  On  the  whole  gelatine  should  not  be  used  in  the  investigation 
of  swine  plague. 

On  nutrient  agar  prepared  in  the  ordinary  way  with  peptone  bouillon 
and  kept  in  the  thermostat,  multiplication  goes  on  rapidly,  so  that  in 
24  hours  the  deep  colonies  are  one-eighth  to  one-fourth  millimetre  in 
diameter  according  to  the  proximity  of  the  colonies  to  one  another  (see 
Plate  xn,  Figs.  1  and  2).  The  deep  or  submerged  colonies  appear 
roundish  or  lenticular,  and  when  examined  under  a  low  power  (about 
60  diameters)  they  are  brownish,  opaque,  with  margin  and  surface  beset 
with  small  knobs,  thus  giving  the  disk  a  reticulated  and  the  border 
an  irregular  wavy  appearance.  Some  colonies  do  not  present  this 
appearance,  but  remain  smooth  on  surface  and  margin.  The  surface 
colonies  are  glistening,  slightly  convex,  whitish  disks,  barely  trans- 
lucent. They  are  circular,  with  margin  having  no  irregularities. 
Under  a  low  power  the  central  portion  is  brownish,  granular,  towards 
the  margin  becoming  more  homogenous  and  translucent  and  exhibit- 
ing usually  very  delicate  radial  striations.  The  deep  colonies  may 
attain  a  diameter  of  one-half  to  three-fourths  millimetre;  the  surface 
colonies,  when  1  centimetre  apart,  measure  4  to  5  millimetres  in  diameter. 
As  in  the  case  of  other  bacteria,  the  size  of  the  colonies  varies  inversely 
as  their  number  on  the  plate. 

A  very  characteristic  feature  of  such  plates  is  the  strong,  disagree- 
able, pungent  odor  which  is  emitted.  This  is  best  detected  when  the 
agar  plates  have  been  prepared  in  so-called  double  dishes,  and  these 
are  quickly  opened  after  they  have  been  closed  for  24  hours  or  less. 
When  the  growth  is  abundant  this  odor  persists  even  after  repeated 
exposure  of  the  plates. 

On  the  inclined  surface  of  nutrient  agar  in  tubes,  the  growth  may 
appear  either  in  the  form  of  isolated  colonies  or  as  a  single  grayish  trans- 
lucent patch,  depending  on  the  number  of  bacteria  rubbed  upon  the 
surface  originally.  (See  Plate  xn,  Fig.  4.)  The  condensation  water 
collected  in  the  bottom  is  usually  quite  turbid  within  24  hours.  After 
two  or  more  weeks  it  will  be  found  that  the  growth  in  the  water  has 
assumed  a  viscid  gelatinous  consistency,  so  that  it  tends  to  come  away 
in  a  mass  when  a  platinum  loop  is  introduced.  This  has  been  charac- 
teristic of  all  swine-plague  germs  thus  far  examined. 

Bouillon  containing  from  one- fourth  to  1  per  cent,  peptone  becomes 


89 

uniformly  but  very  faintly  clouded  within  24  hours.  From  some  out- 
breaks the  growth  may  be  at  first  flocculent  or  granular.  The  bacteria 
grow  in  clumps,  leaving  the  liquid  unclouded.  This,  however,  is  no 
permanent  character,  since  cultures  of  succeeding  generations  after  a 
time  become  uniformly  clouded.  Not  infrequently  a  partial  membrane 
or  a  ring  growth  on  the  glass  at  the  surface  of  the  liquid  appears  after 
one  or  more  weeks  of  quiet  standing  in  a  uniform  temperature.  In 
the  bottom  a  deposit  forms  during  this  time  which  may  become  quite 
viscid.  No  marked  changes  in  reaction  occur  in  the  cultures  even  after 
some  weeks  of  multiplication.  There  seems,  however,  to  be  a  slight 
tendency  toward  the  production  of  an  acid  reaction  in  culture  liquids 
originally  alkaline.  No  fermentation  of  sugars  accompanied  by  the 
liberation  of  gases  takes  place.  In  this  particular  these  bacteria  are 
distinguished  from  hog-cholera  bacilli,  which  are  able  to  cause  fermen- 
tation of  glucose  with  liberation  of  hydrogen  and  carbonic  dioxide.* 

Milk  inoculated  undergoes  no  changes  visible  to  the  naked  eye.  The 
reaction  becomes  faintly  acid.  On  the  surface  of  boiled  potato  there 
is  no  appreciable  multiplication.  I  have  once  or  twice  observed  a  very 
faint  whitish  growth  which  may  have  been  due  to  the  culture  material 
transferred.  In  general,  however,  swine-plague  bacteria  do  not  grow 
on  potato. 

The  temperature  range  for  the  multiplication  of  swine-plague  bac- 
teria may  be  placed  between  65°  and  108°  F.  The  growth  is  very 
feeble  between  65°  and  70°  F.,  and  most  rapid  and  abundant  be- 
tween 97°  to  100°  F.  The  nature  of  the  culture  media  seems  to  have 
some  effect.  If  this  is  very  favorable  multiplication  may  take  place  at 
a  slightly  lower  temperature  than  when  less  favorable. 

Among  the  properties  of  the  group  of  swine-plague  bacteria  pointed 
out  by  German  observers,  and  valuable  as  a  means  of  diagnosis,  is  the 
capacity  to  form  in  culture  liquids  indol  (C8H7N)  and  phenol  or  car- 
bolic acid  (C6H6O).  Both  substances  are  also  formed  ordinarily  during 
the  decomposition  of  albumins,  and  hence  are  present  in  the  intestinal 
tract. 

The  method  followed  in  testing  for  these  substances  is  that  sug- 
gested by  Lewandowski,t  which  consists  in  distilling  the  culture  liquid, 
say  250  cubic  centimetres  of  ordinary  peptone  bouillon  in  which  the 
bacteria  have  grown  for  10  days,  with  50  cubic  centimetres  of  strong 
chlorhydric  acid  and  testing  the  first  portions  of  the  distillate  for  indol 
and  phenol  separately.  For  indol  2  cubic  centimetres  of  a  25  per  cent 
solution  of  sulphuric  acid  is  added  to  5  cubic  centimetres  of  the  distil- 
late, and  then  2  to  3  drops  of  a  0.1  per  cent  solution  of  sodium  nitrite. 
A  red  coloration  indicates  the  presence  of  indol.  A  fine  crystalline 
precipitate  forming  immediately,  or  soon  after  the  addition  of  bromine 
water  to  the  distillate,  indicates  the  presence  of  phenol. 

*  See  foot-note,  p.  81. 

t  Deutsche  med.  Wochenschrift.     1890,  S.  1186. 


90 

The  method  followed  by  the  writer  was  practically  the  sarae,  except- 
ing that  potassium  nitrite  was  used,  the  solution  being  prepared  fresh 
each  time.  A  preliminary  trial  having  shown  phenol  in  most  cultures, 
but  only  a  trace  of  indol  in  one  culture,  a  second  test  was  made. 

Slightly  alkaline  bouillon  containing  1  per  cent  peptone  and  one-half  per  cent  salt 
was  sterilized  in  flasks  containing  200  cubic  centimetres  each,  and  inoculated  May 
15,  1891,  with  swine-plague  bacteria  from  the  following  sources : 

1.  Outbreak  VII. 

2.  Outbreak  VIII. 

3.  Outbreak  IX. 

4.  German  swine  plague  (virulent  variety). 

These  cultures  were  allowed  to  remain  in  the  thermostat  until  June  8,  at  which 
time  they  were  tested  according  to  the  method  indicated. 

The  culture  from  VII  had  an  abundant  viscid  growth  on  the  surface  attached  to 
glass.  Liquid  turbid  when  shaken,  faintly  alkaline ;  odor  disagreeable  and  charac- 
teristic of  swine-plague  cultures.  Slight  precipitate  of  tribromphenol;  no  iudol 
reaction. 

The  culture  from  VIII  had  a  thick  membrane  on  the  surface,  somewhat  viscid. 
Other  characters  as  in  preceding  case.  Phenol  less  abundant.  No  indol. 

The  culture  from  IX  like  that  of  VIII.  Phenol  very  abundant.  Very  faint  indol 
reaction. 

The  culture  of  German  swine  plague  gave  nearly  as  much  precipitate  of  tribrom- 
phenol crystals  as  the  preceding,  but  no  indol  reaction. 

Various  cultures  of  hog-cholera  bacilli  tested  showed  the  presence  of  neither  indol 
nor  phenol. 

The  reason  why  the  indol  reaction  failed  in  our  hands  is  not  clear. 
It  may  be  that  as  the  culture  grows  older  the  phenol  reaction  increases 
while  the  indol  reaction  may  disappear.  It  will  be  noted  that  phenol 
was  detected  in  all  four  cultures,  in  the  third  in  abundance.  The  crystals 
of  tribromphenol  examined  microscopically  were  identical  in  all  four 
cases.  It  might  also  be  mentioned  that  the  second  culture,  inoculated 
with  the  least  virulent  swine-plague  bacteria,  contained  the  smallest 
quantity  of  phenol. 

RESISTANCE  OF   SWINE-PLAGUE  BACTERIA  TO  DESTRUCTIVE  AGENTS. 

Swine-plague  bacteria  possess  less  power  to  resist  destructive  agents 
than  hog-cholera  bacilli.  Their  life,  even  under  what  might  be  regarded 
as  the  most  favorable  conditions,  is  brief.  In  the  laboratory  cultures  are 
liable  to  die  out  in  3  or  4  weeks,  especially  when  evaporation  is  going 
on.  In  bouillon  but  2  or  3  days  old  the  large  majority  of  bacteria  are 
dead,  for  if  plate  cultures  be  made  from  the  liquid  only  very  few  colo- 
nies appear  where  we  would  expect  thousands.  The  resistance  to  dry- 
ing is  feebler  than  that  of  hog-cholera  bacilli.  In  the  report  for  1886, 
some  experiments  are  reported  which  show  that  drops  from  a  bouillon 
culture  dried  on  cover  glasses  failed  to  infect  fresh  tubes  on  and  after  3 
days.  Shorter  periods  were  not  tried  in  this  experiment. 

In  another  trial  with  peritoneal  exudate  from  a  rabbit  containing  im- 
mense numbers  of  swine-plague  bacteria  dried  on  cover  glasses,  bouillon 
tubes  were  infected  up  to  the  third  day,  but  not  thereafter. 


91 

In  the  report  for  1887-'88,  p.  143,  some  additional  experiments  are 
given  with  swine  plague  bacteria  from  Iowa.  Bacteria  in  bouillon  cul- 
tures, dried  for  a  period  longer  than  36  hours,  were  destroyed,  while 
bacteria  from  agar  cultures  lived  for  6  days.  The  difference  is  very 
likely  due  to  the  thickness  of  the  dried  film,  which  is  much  greater  when 
material  from  agar  cultures  is  employed,  owing  to  the  density  of  the 
growth. 

They  are  likewise  more  easily  destroyed  by  disinfectants  than  are  hog 
cholera  bacilli.  Hence  the  extended  experiments  made  in  connection 
with  our  study  of  hog-cholera  bacilli  have  made  a  repetition  of  such 
experiments  with  swine  plague  unnecessary.  We  simply  give  the  fol- 
lowing experiments  with  lime,  since  this  disinfectant  is  cheap,  efficient, 
and  easily  applied. 

April  18,  1891.  Five  cubic  centimetres  of  limewater  is  thoroughly  mixed  with  a 
loop  of  agar  growth  of  swine-plague  bacteria  1  day  old  from  outbreak  IX.  Bouillon 
tubes ;  inoculated  with  a  loop  of  this  suspension  after  45  minutes,  1,  2,  3,  and  6  hours, 
remain  clear. 

This  experiment  was  repeated  with  the  modification  that  two  loops  of  agar  growth 
were  mixed  with  the  liuiewater  and  bouillon  tubes  were  inoculated  immediately  after 
making  the  mixture,  and  after  5, 10, 15, 20, 25, 30, 40, 50,  and  60  minutes.  All  but  the 
first  tube  remained  clear. 

The  limewater  in  a  third  trial  was  diluted  with  two  volumes  of  water,  and  therefore 
contained  but  0.04  per  cent  of  lime  approximately.  In  this  series  all  but  the  tube, 
inoculated  immediately  after  the  bacteria  were  mixed  with  the  limewater,  remained 
clear. 

These  experiments  show  that  as  weak  a  solution  of  limewater  as  0.04 
per  cent  is  sufficient  to  destroy  swine-plague  bacteria  almost  imme- 
diately. 

The  rapidity  with  which  swine-plague  bacteria  are  destroyed  by  dry- 
ing and  other  agencies  made  it  very  probable  that  their  life  in  the  su- 
perficial layers  of  the  soil  where  they  are  deposited  must  be  very  brief. 
The  following  simple  experiments  place  this  supposition  beyond  doubt, 
for  they  show  that  rabbits  can  no  longer  be  infected  after  the  bacteria 
have  been  in  the  soil  for  a  period  of  8  to  10  days. 

March  7,  1888.  A  pot  of  sterilized  soil  was  inoculated  by  pouring  upon  its  surface 
50  cubic  centimetres  of  a  beef-infusion  peptone  culture  which  had  been  growing  for 
24  hours  at  95°  F.  The  pot  was  kept  in  the  laboratory,  covered  with  a  disinfected 
bell  jar.  March  10  a  rabbit  was  inoculated  with  one-fourth  cubic  centimetre  of 
sterile  beef  infusion  in  which  a  little  soil  had  been  stirred  up.  The  rabbit  died  in  48 
hours  with  numerous  polar-stained  swine-plague  bacteria  in  the  internal  organs. 
Ten  and  fourteen  days  respectively  after  the  soil  had  been  infected  two  other  rabbits 
were  Inoculated  from  the  same  soil.  Both  remained  well. 

March  29.  A  pot  of  soil  was  inoculated  by  pouring  upon  its  surface  100  cubic  centi- 
metres of  a  beef-infusion  peptone  culture  2  days  old  of  swine-plague  bacteria  obtained 
through  Prof.  W.  H.  Welch  from  an  outbreak  studied  by  him  in  1887  in  Baltimore, 
Md.  The  pot  was  sunk  into  a  larger  pot  filled  with  sterilized  soil  and  the  whole 
buried  in  the  garden  of  the  Department  of  Agriculture  on  a  level  with  the  soil.  To 
teat  the  virulence  of  the  culture  used  to  infect  the  soil  a  rabbit  was  inoculated  in  the 
ear  with  a  lancet  dipped  into  it.  It  died  within  48  hours.  Cover-glass  preparations 
and  cultures  reveal  the  inoculated  bacteria  in  the  internal  organs.  Four  days  later, 


92 


a  rabbit  was  inoculated  from  the  soil  as  in  the  preceding  experiment.  The  rabbit 
died  within  2  days.  No  bacteria  found  on  coyer-glass  preparations ;  cultures  contain 
several  kinds  of  bacteria.  Swine-plague  bacteria  not  detected.  This  case  was  there- 
fore doubtful.  April  7,  nine  days  after  the  infection  of  the  soil,  another  rabbit  was 
inoculated  therefrom.  This  one  remained  well. 

Some  experiments  made  in  1886  indicated  a  rapid  destruction  of  swine- 
plague  bacteria  in  sterilized  water.  In  1888  and  1889  Dr.  V.  A.  Moore 
was  charged  to  carry  out  another  series  of  experiments  to  test  this 
problem  more  thoroughly. 

In  the  first  experiment  a  platinum  loop  rubbed  over  the  surface  growth  of  an  agar 
culture  24  hours  old  was  stirred  up  in  10  cubic  centimetres  sterilized  Potomac  water 
and  placed  in  the  laboratory.  A  second  tube  of  water  prepared  in  the  same  way  was 
placed  in  the  refrigerator  (50°-55°  F.). 

From  the  first  tube  1  cubic  centimetre  transferred  to  bouillon  on  the  fifth  day  failed 
to  infect  it.  From  the  second  tube  the  same  quantity  failed  to  infect  a  bouillon  tube 
on  the  seventh  day. 

In  a  second  series  two  tubes  of  water  were  infected,  each  with  three  loops  of  surface 
growth  and  three  drops  of  condensation  water  from  an  agar  culture.  It  will  be 
noted  that  in  this  case  some  nutritive  substances  must  have  been  transferred  iu  the 
condensation  water.  Bouillon  tubes  were  infected  up  to  the  thirty  fifth  day  from  the 
water  in  the  laboratory.  From  that  in  the  refrigerator  a  successful  inoculation  was 
made  on  the  nineteenth  day,  but  it  failed  after  38,  41,  and  44  days. 

A  third  series  was  tried.  Each  of  two  tubes  was  infected  with  three  loops  of  growth 
from  an  agar  culture  1  day  old.  From  the  one  in  the  laboratory  inoculation  with  1 
cubic  centimetre  failed  on  the  ninth  day ;  from  the  one  in  the  refrigerator,  after  the 
twentieth  day. 

Swine-plague  bacteria  in  water  containing  no  nourishment  may  thus 
succumb  in  7  to  10  days  at  ordinary  temperatures  (60°-70°F.).  When 
some  nutritive  substances  are  present  this  period  may  be  materially 
lengthened.  In  lower  temperatures  the  bacteria  seem  to  live  somewhat 
longer.  A  comparison  between  the  relative  vitality  of  hog-cholera  and 
swine-plague  bacteria  may  be  tabulated  as  follows : 


Swine  plague. 

Hog  cholera. 

Destroyed  by  moist  heat  at  58°  C  

7  minutes  
1J  to  2  days  .  

15  minutes. 
7  to  9  days. 

Destroyed  by  drying  (from  agar)  

After  6  days.  .  . 
After  10  iliiy.s 

After  4  months. 
After  ii  to  4  mouths. 

Destroyed  insoil  

After  4  days  ... 

After  2  to  3  months. 

THE  PATHOGENIC  ACTION  OF  SWINE-PLAGUE  BACTERIA. 

EFFECT  ON  SMALL  ANIMALS. 

In  order  to  understand  best  the  pathogenic  action  of  swine-plague 
bacteria  a  brief  account  of  the  results  of  inoculation  into  smaller  ani- 
mals will  be  given  before  the  disease  in  swine  is  discussed.  These  in- 
oculations being  made  with  pure  cultures  the  effects  are  exhibited  in  a 
clearer  manner  than  in  swine  in  which  hog  cholera  is  so  frequently  an 
associated  disease. 

The  various  inoculations  into  the  smaller  animals,  such  as  mice,  rab- 
bits, guinea-pigs,  pigeons,  and  fowls,  are  briefly  described  in  connection 
with  the  special  outbreaks  from  which  the  bacteria  were  obtained.  In 
the  present  chapter  only  the  general  results  will  be  brought  together 
and  broadly  outlined  in  their  bearing  on  swine  plague. 

If  we  take  the  inoculation  of  rabbits  as  a  starting  point  we  find  that 
there  are  different  degrees  of  virulence  or  pathogenic  activity  very 
clearly  brought  out.  Thus  the  swine- plague  bacteria  obtained  from  out- 
breaks VII  and  IX,  and  from  Germany,*  Were  of  the  maximum  degree 
of  virulence  so  far  as  rabbits  are  concerned,  inasmuch  as  the  latter 
died  16  to  20  hours  after  inoculation  with  very  minute  doses  of  culture 
material.  The  blood  and  the  various  organs  contained  often  immense 
numbers  of  the  inoculated  bacteria,  always  exhibiting  the  very  charac- 
teristic polar  stain  shown  in  Plate  xi,  Fig.  1.  These  bacteria  were  thus 
able  to  produce  a  rapidly  fatal  septicaemia. 

The  bacteria  from  some  of  the  other  outbreaks  (such  as  I,  II,  IV,  V, 
and  VIII)  were  not  so  virulent.  The  rabbits  inoculated  under  the  skin 
died  from  40  hours  to  7  days  after  inoculation.  In  many  such  cases 
the  acute  septicaemia  was  no  longer  present,  but  a  peritonitis  quite 
invariably  appeared.  In  the  more  rapidly  fatal  cases  this  was  hemor- 
rhagic;  in  the  others  a  considerable  amount  of  grayish,  sometimes  quite 
viscid,  exudation  had  taken  place.  This  covered  the  caecum,  liver,  and 
spleen  with  a  thin  pseudo-membrane,  and  was  found  to  some  extent 
between  the  coils  of  the  large  intestine.  The  exudate  consisted  of  leu- 
cocytes, fibrin,  and  immense  numbers  of  bacteria.  The  relative  propor- 
tions of  these  elements  varied  according  to  the  age  of  the  disease,  the 
leucocytes  being  most  abundant  in  the  advanced  stages.  The  swine- 
plague  bacteria  were  localized  more  or  less  in  the  peritoneal  cavity. 
The  spleen  and  liver  and  the  blood  contained  very  few. 

*  For  experiments  with  cultures  of  the  Germau  swine  plague  see  pp.  127-129. 

93 


94 

The  coarse  of  the  disease  did  not  always  correspond  to  this  descrip- 
tion. In  a  small  number  of  instances  the  subcutaneous  inoculation  was 
followed  not  by  peritonitis  but  by  pleuritis  and  pericarditis.  The  exudate 
into  these  serous  sacs  was  of  the  same  nature  as  the  peritoneal  exudate 
in  other  cases.  More  rarely  the  pleuritis  was  accompanied  by  a  genuine 
pneumonia  of  a  croupous  character. 

A  third  form  of  the  inoculation  disease  is  produced  by  very  attenu- 
ated swine-plague  bacteria.  This  attenuation  may  have  been  due  to 
long  cultivation  in  the  laboratory  or  else  it  may  have  taken  place  in  na- 
ture. The  rabbits  inoculated  subcutaneously  may  live  several  weeks. 
The  place  of  inoculation  becomes  the  starting  point  of  a  partly  hemor- 
rhagic,  partly  purulent  infiltration  and  thickening  of  the  skin  and 
subcutaneous  connective  tissue  which  may  extend  over  the  entire 
abdomen  and  thorax.  The  skin  in  places  may  become  necrotic,  dry, 
and  hard.  If  the  animal  survives,  which  is  not  infrequently  the  case, 
the  inflammation  becomes  circumscribed  into  an  abscess  which  finally 
heals.  In  these  cases  internal  changes  such  as  peritonitis  and  pleuritis 
are  absent.  In  some  cases,  however,  a  parenchymatous  and  fatty  de- 
generation of  the  heart  muscle  and  the  kidneys  is  present. 

Such  attenuated  bacteria  are  still  capable  of  producing  all  the  vari- 
ous lesions  ascribed  to  the  more  virulent  varieties  when  injected  directly 
into  the  circulation.  This  is  very  easily  done  by  choosing  a  vein  of  the 
ear.  After  such  injection  we  may  produce  a  rapidly  fatal  septicaemia,  or 
inflammation  of  the  serous  membranes,  according  to  the  quantity  of 
virus  injected  and  the  relative  virulence.  The  localization  is  the  same 
as  with  subcutaneous  inoculations.  In  rare  cases  even  intravenous 
injections  of  small  doses  do  not  prove  fatal,  and  then  we  may  observe 
further  localization  of  the  virus  in  the  joints  of  the  extremities,  chiefly 
the  lower,  or  even  in  the  subcutaneous  and  interinuscular  connective 
tissue  in  different  parts  of  the  body.  Such  localizations  were  in  a  state 
of  suppuration  when  they  came  to  our  notice. 

It  might  be  maintained  that  the  attenuated  swine-plague  bacteria, 
such  as  those  from  outbreaks  VIII  and  X,  were  specifically  different 
from  the  very  virulent  varieties  obtained  from  outbreaks  YII  and  IX, 
owing  to  the  differences  in  the  rabbit  disease  produced  by  them.  We 
have,  however,  carried  out  experiments  which  dispose  of  this  possible 
objection.  By  making  rabbits  more  insusceptible  to  the  virus  of  swine 
plague  by  vaccination  we  have  been  able  to  vary  the  disease  produced 
by  virulent  varieties  so  as  to  produce  nearly  all  the  forms  caused  by 
attenuated  varieties.  For  example,  those  bacteria  (IX)  which  produce 
a  rapidly  fatal  septicaemia  have,  in  vaccinated  rabbits,  produced  a  pro- 
longed disease  characterized  in  some  cases  only  by  local  reaction  at  the 
point  of  inoculation  and  recovery,  in  others  by  peritonitis  or  pleuritis 
and  pneumonia.  The  two  following  cases  are  interesting  illustrations : 

Rabbit  No.  19  received  into  an  ear  vein  about  13  cubic  centimetres 
of  bouillon  culture  of  swine-plague  bacteria,  sterilized  at  58°  0.,  in  five 


95 

closes  at  periods  3  to  4  days  apart.  Oil  May  26,  1891,  5  days  after  the 
last  injection,  it  was  inoculated  subcutaueously  with  one  five-hundredth 
cubic  centimetre  of  a  bouillon  culture  of  living  swine-plague  bacteria. 
While  a  check  rabbit  (not  treated)  died  within  20  hours  after  inocula- 
tion, this  rabbit  died  at  noon  June  2,  i.e.,1  days  after  inoculation.  The 
skin  and  subcutis  at  the  point  of  inoculation  extensively  thickened  by 
purulent  infiltration.  Double  exudative  pleuritis  and  pericarditis  with 
large  pneumonic  regions  in  both  lungs  in  which  the  hepatization  had  ad- 
vanced to  the  gray  stage.  Bits  of  this  lung  tissue  examined  fresh  were 
made  up  chiefly  of  leucocytes.  Swine-plague  bacteria  in  exudate  and 
spleen. 

Two  other  rabbits  treated  with  one  additional  injection  of  sterilized 
bouillon  cultures  had  considerable  local  swelling  after  the  test  inocula- 
tion, but  both  recovered. 

Another  set  of  four  rabbits  were  treated  with  sterilized  agar  cultures 
suspended  in  bouillon.*  Only  one  succumbed  to  the  test  inoculation 
in  6  days,  while  a  fresh  rabbit  succumbed  to  the  same  inoculation  (one 
five-hundredth  cubic  centimetre  bouillon  culture  of  swine-plague  bac- 
teria from  outbreak  IX)  in  20  hours.  The  lesions  in  the  vaccinated 
rabbit  were  extensive  local  subcutaneous  infiltration,  double  purulent 
pleuritis  and  pericarditis,  and  congestion  of  both  lungs. 

The  numerous  bacteria  in  the  exudate  were  not  attenuated,  for  a  rab- 
bit inoculated  with  a  particle  from  the  pleural  cavity  died  within  20 
hours. 

An  exceedingly  interesting  element  in  these  results  is  the  tendency 
of  the  swine-plague  bacteria  towards  the  production  of  disease  of  the  lungs 
and  serous  membranes  in  these  treated  rabbits.  The  vaccination  they  have 
undergone  has  placed  them  nearer  the  pig  as  regards  insusceptibility. 

A  great  variety  of  pathological  conditions  is  thus  produced  by  differ- 
ent degrees  of  viruleuce  of  the  same  species  of  bacteria,  the  significance 
of  which  will  be  appreciated  when  we  come  to  the  disease  in  swine.  If 
we  would  arrange  the  various  lesions  according  to  their  fatality,  the  sep- 
ticaemia or  multiplication  of  bacteria  in  the  blood  stands  first.  Next 
come  peritonitis,  pleuritis,  and  pericarditis  with  or  without  pneumonia, 
and  lastly  joint  disease. 

The  relative  virulence  of  swine-plague  bacteria  from  different  sources 
thus  demonstrated  on  rabbits  has  its  counterpart  in  the  relative  viru- 
lence of  the  same  bacteria  with  reference  to  different  species  of  animals' 
The  susceptibility  of  the  animals  used  Is  greatest  in  rabbits  and  gray 
mice,  and  diminishes  in  guinea-pigs,  pigeons,  and  fowls  in  the  order 
given. 

In  guinea  pigs  the  lesions  produced  by  subcutaneous  inoculation 
present  the  various  forms  which  we  have  seen  characteristic  of  rabbits. 
There  is  this  difference,  however,  that  the  more  attenuated  varieties 
are  likely  to  have  no  effect  on  guinea-pigs  beyond  a  slight  local  reaction. 

*  See  p.  148  for  details. 


96 

In  pigeons  and  fowls  the  inoculation  disease  is  a  septicaemia,  produced, 
however,  only  by  the  most  virulent  varieties  of  swine-plague  bacteria. 
Attenuated  varieties  have  no  effect. 

We  have  seen  that  the  bacteria  from  outbreaks  VII  and  IX,  and 
from  Germany,  all  produce  a  rapidly  fatal  septicaemia  in  rabbits,  and  in 
so  far  no  difference  in  their  pathogenic  power  is  manifest.  But  the 
guinea-pig  inoculations  make  a  discrimination  in  showing  that  the  bac- 
teria from  VII  are  less  virulent  than  those  from  IX.  Inoculation  with 
the  latter,  even  in  very  minute  doses  (see  p.  76),  produces  a  rapidly 
fatal  septicaemia,  and  heuce  the  effect  on  rabbits  and  guinea-pigs  is 
alike.  Inoculation  with  cultures  from  VII  are  on  the  other  band  fatal 
to  guinea-pigs  only  after  some  days,  and  the  localizations  are  uncertain 
just  as  with  attenuated  swine-plague  bacteria  in  rabbits.  The  inocula- 
tion of  pigeons  also  shows  this  difference.  Bacteria  from  VII  are  fatal 
only  when  the  injections  are  made  slightly  into  tbe  muscular  tissue. 
The  bacteria  from  IX  are  fatal  in  24  hours,  even  when  a  very  minute 
quantity  of  the  culture  is  placed  under  the  skin. 

In  case  of  fowls  neither  variety  of  bacteria  is  fatal  when  introduced 
under  the  skin.  When,  however,  the  needle  punctures  the  pectoral 
muscle  the  bacteria  IX  prove  fatal  in  36  to  48  hours.  With  pigeons  the 
case  is  similar.  Bacteria  which  fail  to  produce  any  effect  when  placed 
under  the  skin  may  still  prove  fatal  when  injected  into  the  muscular 
tissue. 

A  further  discrimination  is  possible  in  still  more  refractory  animals, 
such  as  swine.  It  has  been  shown  in  the  preceding  pages  that  swine- 
plague  bacteria  from  outbreak  IX  are  the  most  virulent  which  haveyet 
been  encountered.  One  of  the  cultures  of  the  German  swine  plague  is 
still  more  virulent,  since  it  proves  fatal  to  swine  after  subcutaneous  in- 
oculation, while  the  American  variety  usually  fails. 

The  nature  of  the  pathogenic  activity  of  swine-plague  bacteria  is  to 
a  certain  extent  cleared  up  by  these  experimental  inoculations.  When 
they  are  capable  of  multiplying  in  the  blood  they  produce  speedy  death, 
probably  by  the  development  of  some  poison  and  by  a  modification  of 
the  blood.  When  multiplication  in  the  blood  does  not  take  place,  the 
large  serous  cavities  still  permit  their  growth  on  the  lining  membranes. 
The  irritation  thus  set  up  induces  a  fibriuous  and  cellular  exudation, 
which  later  on  becomes  completely  cellular.  The  means  by  which  the 
bacteria  are  destroyed  in  these  cavities  when  recovery  ensues  is  not 
known.  Phagocytosis  probably  plays  an  important  role  here,  for  I  have 
frequently  seen  large  numbers  of  bacteria  imbedded  in  the  protoplasm 
of  the  leucocytes.  The  pleural  cavity  is  less  frequently  involved.  This 
may,  however,  be  due  in  part  to  the  fact  that  in  most  cases  the  inocula- 
tions were  made  in  the  region  of  the  abdomen  or  the  thigh. 

The  relative  virulence  of  the  varieties  investigated  thus  varies  con- 
siderably. Of  those  studied  in  detail  recently  the  highest  degree  of 
virulence  would  belong  to  one  form  of  the  German  swine  plague.  The 
others  may  be  arranged  in  the  following  order :  IX,  VII,  VIII  and  X, 


97 

THE    DISEASE    IN    SWINE    AS    PRODUCED    BY    THE    INOCULATION    OP 

CULTURES. 

In  order  to  determine  the  effect  of  pure  cultures  swine  were  inocu- 
lated under  the  skin,  into  the  veins,  into  the  lungs,  and  into  the  abdom- 
inal cavity.  They  were  also  fed  with  cultures  and  with  the  viscera 
of  small  animals  which  had  succumbed  to  inoculation.  The  details  of 
these  experiments  have  been  given  under  the  different  outbreaks,  and 
it  now  simply  remains  to  bring  the  facts  together. 

It  is  at  once  apparent  that  any  method  of  inoculation  whatever-can 
merely  approximate  the  conditions  prevailing  in  outbreaks  of  disease. 
The  body  receives  in  the  one  case  a  large  number  of  bacteria  at  one 
time,  while  in  the  natural  disease  animals  are  being  constantly  infected 
by  small  quantities.  A  single  small  dose  frequently  repeated — and  this 
is  what  actually  takes  place  in  an  infected  herd — may  produce  far  more 
serious  results  than  a  single  large  dose.  Again,  the  repetition  of  small 
doses  may  produce  a  disease  quite  different  in  character  from  that  pro- 
duced by  a  single  large  dose  of  the  virus;  finally,  the  ways  in  which 
bacteria  enter  the  body,  in  the  natural  disease,  vary  greatly,  and  differ 
in  most  respects  from  the  ways  in  which  they  are  introduced  experi- 
mentally. 

These  and  many  more  considerations  which  need  not  be  discussed  here, 
serve  to  show  that  with  inoculations  into  swine  we  may  attempt  but 
imperfectly  two  objects,  first,  to  demonstrate  that  the  bacteria  under  in- 
vestigation do  actually  produce  disease,  and,  second,  that  they  may  have 
a  predilection  for  certain  organs  and  tissues  of  the  body  where  certain 
kinds  of  lesions  are  produced. 

The  inoculations  in  swine  produce  practically  the  same  lesions  as 
those  which  follow  the  inoculations  of  the  smaller  animals.  Here  we 
observe  variations  in  the  localization  of  the  injected  bacteria  similar  to 
those  produced  by  attenuated  cultures  in  rabbits  and  guinea-pigs. 

Feeding  cultures  and  viscera  of  inoculated  rabbits  has  thus  far 
proved  negative. 

Subcutaneous  inoculation  has  in  most  cases  proved  negative  except- 
ing with  bacteria  from  outbreaks  I,  II,  and  IX.  One  variety  of  the 
German  swine-plague  bacteria  proved  in  most  cases  fatal  after  subcu- 
taneous inoculation.*  This,  as  has  been  stated  before,  gives  them  a 
higher  potency  than  any  American  variety  thus  far  encountered. 

Injection  of  cultures  into  the  circulation  is  usually  fatal  when  viru- 
lent varieties  are  employed.  These  lesions  depend  upon  the  time  elaps- 
ing between  inoculation  and  death,  which  in  turn  varies  according  to  the 
virulence  and  the  quantity  of  culture  liquid  injected.! 

When  the  animals  die  within  one  or  two  days  the  visible  changes  are 
confined  to  the  blood,  and  in  some  cases  extend  to  the  peritoneum  and 

*  See  p.  93. 

t  A  full  account  of  these  inoculations  is  given  on  pages  71-75. 
1C14 7 


98 

plenra,  which  are  inflamed  and  covered  with  more  or  less  exudation. 
If  the  animals  live  longer  these  changes  become  more  accentuated,  and 
in  several  cases  portions  of  the  lungs  become  hepatized.  This  hepatiza* 
tion  may  be  looked  upon  as  secondary  to  the  pleuritis,  as  in  case  of  the 
rabbits  having  similar  lesions.  In  two  cases  the  bacteria  became  local- 
ized in  various  joints  of  the  body,  where  necrosis  of  bones  and  suppura- 
tion took  place.  Intermuscular  collections  of  pus  were  also  observed. 
The  duration  of  the  disease  in  these  cases  was  several  weeks  or  longer. 
Other  organs,  excepting  the  pericardium,  in  one  of  these  animals,  were 
not  directly  affected. 

When  the  bacteria  are  injected  directly  into  the  lung  tissue  through 
the  chest  wall,  death  may  follow  within  16  to  24  hours,  or  life  may  be 
prolonged  and  severe  pleuritis  and  pericarditis  associated  with  hepati- 
zation  of  the  lung  tissue,  may  appear.  Thus  in  pig  275  (see  Plate  vi) 
though  the  injection  was  made  into  the  right  lung,  as  a  result  the  major 
portion  of  the  left  lung  also  was  involved  in  pneumonia. 

In  a  few  experimental  cases  the  intestines  were  involved.  In  one 
case,  as  a  result  of  the  peritonitis  following  an  intra-abdomiual  injec- 
tion, the  walls  of  the  small  intestine  were  swollen,  inflamed,  and  a 
copious,  friable,  yellowish  exudate  had  formed  on  the  deeply  inflamed 
mucosa.  In  another  case  all  Peyer's  patches  in  the  small  intestine  were 
swollen,  very  hypersemic,  and  in  part  hemorrhagic,  In  tense  hypenemia 
of  the  mucosa  of  the  stomach  has  been  observed  in  several  cases,  both 
after  intravenous  and  intrathoracio  inoculation, 

SWINE  PLAGUE  AS   OBSERVED    IN  EPIZOOTICS, 

The  variety  of  lesions  produced  by  the  inoculation  of  swine-plague 
bacteria  is  by  no  means  so  great  as  that  observed  in  nature.  While 
there  are  outbreaks  in  which  considerable  uniformity  is  observed,  there 
are  others  in  which  each  animal  is  a  surprise  to  the  pathologist.  In 
general  it  may  be  stated  that  the  lungs  and  the  digestive  tract  are  the 
chief  seats  of  the  disease,  though  other  organs,  notably  the  lymphatic 
glands,  are  secondarily  involved.  The  disease  is  localized  in  the  lungs 
and  the  digestive  tract  most  likely  because  the  bacteria  gain  entrance 
through  the  respiratory  and  digestive  passages. 

The  lungs  have  been  found  diseased  in  nearly  every  outbreak  which 
has  been  investigated.  In  some  (notably  IV,  VII,  and  VIII)  the  lung 
disease  is  the  predominating  affection  and  the  direct  cause  of  death. 
In  IX  pneumonia  was  absent  in  some  cases,  but  pleuritis  and  interlob- 
ular  oedema  were  generally  present.  The  localization  of  the  disease  in 
certain  lobes  of  the  lungs  is  quite  constant.  The  ventral  lobes  are  first 
attacked,  next  come  the  cephalic  and  azygos,  and  lastly  the  principal 
lobes.  This  movement  of  the  disease  seems  to  depend  on  gravity,  inas- 
much as  the  diseased  is  marked  off  from  the  healthy  portion  by  a  nearly 
horizontal  line.  In  other  words,  the  most  dependent  portions  of  the 


99 

lungs  are  the  ones  affected  first,  and  as  the  disease  progresses  upwards 
only  a  small  portion  of  the  principal  lobe,  directly  under  the  back  of  the 
animal,  remains  pervious,  provided  the  life  of  the  animal  is  maintained 
up  to  this  point.  This  localization  of  the  disease  is  indicated  on  Plates 
i  and  n,  in  connection  with  which  a  description  of  these  drawings  will 
be  found.  A  similar  distribution  of  disease  I  have  observed  in  cases  of 
bovine  pneumonia  due  to  bacteria  and  to  actinomyces,  and  in  isolated 
cases  of  pneumonia  in  swine,  the  cause  of  which  I  was  unable  to  trace 
at  the  time.  In  fact,  in  nearly  all  cases  of  pneumonia  in  swine,  except- 
ing a  few  which  were  either  caused  by  lung  worms  or  due  to  embolism, 
the  disease  involved  the  regions  described  and  indicated  on  the  plates 
by  shading.  In  the  exceptions  the  pneumonia  involved  portions  of  the 
principal  lobes  not  contiguous  to  the  veutrals. 

Pathologists  have  defined  two  kinds  of  pneumonia,  croupous  and 
catarrhal  pneumonia,  or  broncho  pneumonia.  In  the  former  the  vesic- 
ular portion  of  the  lung  substance  is  chiefly  affected;  in  broncho- 
pneumonia  the  smaller  bronchioles  are  said  to  be  primarily  affected  and 
the  vesicular  portion  or  alveoli  secondarily.  In  croupous  pneumonia, 
there  is,  following  the  stage  of  congestion,  an  emigration  of  red  blood 
corpuscles,  some  leucocytes,  and  an  exudate  of  fibrin  into  the  alveoli. 
These  elements  are  firmly  matted  together  by  the  coagulating  fibrin, 
making  the  diseased  lung  firm  to  the  touch.  In  broncho-pneumonia 
the  catarrhal  condition  of  the  smalter  air  tubes  makes  them  impervious 
to  air.  The  lung  tissue  which  they  supply  is  gradually  emptied  of  air 
and  assumes  the  appearance  of  red  flesh,  owing  to  the  collapse  of  the 
walls  of  the  alveoli  and  the  distended  condition  of  the  capillary  net- 
work. Subsequently  the  inflammation  extends  into  the  alveoli,  which 
then  become  distended  with  cellular  masses. 

The  definitions  of  pathology  do  not  always  apply  to  classification  of 
lesions  from  tha^standpoint  of  etiology  or  causation.  A  definition  from 
an  anatomical  standpoint  refers  to  a  condition.  The  same  bacteria  may 
under  different  circumstances  produce  a  variety  of  conditions.  Another 
difficulty  meets  us  in  attempting  to  describe  the  lesions  due  to  bacteria 
in  animal  organisms.  The  definitions  have  had  their  origin  in  human 
diseases  and  are  not  always  applicable  to  animal  diseases.  Moreover 
there  is  a  difference  between  different  species  of  animals.  Anyone  who 
has  experimented  with  different  animals  knows  that  they  do  not  react 
exactly  alike  after  inoculation  with  the  same  bacteria.  There  seem  to 
be  certain  peculiarities  belonging  to  each  species  which  have  not  yet 
been  clearly  formulated  by  comparative  pathology.  They  may  be  due 
to  differences  in  anatomical  structure  or  to  physiological  peculiarities. 

It  is  furthermore  evident  that  the  nature  of  the  lung  disease  will  de- 
pend more  or  less  upon  the  mode  of  entrance  of  the  virus.  If  it  can 
enter  only  by  way  of  the  air  tubes  it  will  appear  perhaps  as  a  broncho- 
pneumonia.  If  it  can  enter  the  lung  tissue  through  the  circulation  we 
may  have  more  or  less  scattered  centers  of  hepatization  (embolic  pneu- 


100 

monia).  If  it  can  enter  by  way  of  the  pleura,  the  virus  will  creep  along 
the  interlobular  and  peribronchial  tissue  before  it  invades  the  paren- 
chyma proper. 

In  natural  infection  the  swine-plague  bacteria  enter  the  lung  tissue 
chiefly  by  way  of  the  air  tubes.  At  the  same  time  it  is  not  improbable 
that  occasionally  they  may  enter  the  serous  cavities  first,  i.  e.,  invade 
the  pleural  cavities  and  thence  the  lungs.  This  probability  is  shown 
by  our  inoculations  in  which  intravenous  injections  produced  exudative 
pleuritis,  and  pneumonia  of  the  most  dependent  portions  of  the  lungs 
covered  by  the  pleural  exudate.  It  is  not  improbable  that  even  in  the 
natural  disease  the  bacteria  which  have  gained  access  to  a  portion  of 
the  lung  tissue  by  way  of  the  air  tubes  reach  the  pleura  covering  this 
portion,  and  may  then  by  this  route  invade  other  portions  of  the  lungs. 
It  may  be  that  in  this  way  a  pneumonia  originally  single  may  become 
double.  I  have  also  observed  not  infrequently  that  the  first  pneumonic 
infiltration  of  the  principal  lobe  was  at  the  points  of  contact  with  the 
diseased  ventral  lobe,  and  that  the  resting  of  a  lobe  against  an  inflamed 
serous  surface,  such  as  the  pericardium,  caused  a  pneumonic  infiltration 
at  the  point  of  contact. 

These  facts  go  far  to  show  that  swine -plague  bacteria  may  invade 
the  lungs  both  from  the  air  tubes  and  the  pleural  cavities.  I  am  not 
inclined  to  believe  that  pneumonia  is  produced  to  any  extent  by  swine- 
plague^  bacteria  acting  as  emboli  *in  the  circulation,  because  they  are 
rarely  found  in  the  blood.  Comparative  inoculation  experiments  in  rab- 
bits show  that  the  chief  indication  of  attenuation  is  inability  to  multi- 
ply in  the  blood.  This  probably  holds  with  equal  force  in  swine  whose 
power  of  resistance  is  so  much  greater  than  that  of  rabbits. 

We  may,  therefore,  expect  to  find  the  character  and  seat  of  the  lung 
lesions  somewhat  varia  ble — and  this  is  actually  the  case.  It  would  be 
difficult  to  find  two  lungs  exactly  alike  so  far  as  gross  appearances  go. 
This  to  be  sure  may  be  due  largely  to  the  fact  that  animals  die  in  dif- 
ferent stages  of  the  disease.  Yet  there  are  differences  evidently  not 
dependent  on  this  fact  which  must  be  left  for  special  pathological  in- 
vestigation. 

"After  these  preliminary  remarks  we  turn  to  a  brief  description  of  a 
swine-plague  lung.  In  general  the  cephalic  (anterior)  half  is  hepatized, 
of  a  dark-red  or  grayish-red  color,  firm  to  the  touch.  The  pleura  is  more 
or  less  thickened  and  opaque,  and  covered  with  easily  removable  friable 
false  membranes.  In  the  more  recently  affected  regions  a  faint  but 
quite  regular  delicate  mottling  with  yellow  is  observed  to  shine  through 
the  pleura  when  not  thickened.  These  minute,  hazy,  yellowish  dots 
usually  occur  in  groups  of  four.  Occasionally  whitish  or  yellowish 
patches  varying  much  in  size  are  seen  perhaps  more  frequently  in  the 
ventral  lobes.  These  correspond  to  homogeneous  dead  masses  of  lung 
tissue. 

When  such  lungs  are  cut  into,  the  section  presents  much  the  same 


101 

appearance,  both  as  regards  color,  mottling,  etc.,  as  when  viewed  from 
the  surface,  excepting  that  the  details  are  less  distinct.  In  some  cases 
in  the  most  recently  invaded  territories  in  the  principal  lobe  and  nearer 
the  dorsum  in  the  other  lobes,  the  dark  or  grayish-red  cut  surface  shows 
grayish  lines  usually  arranged  in  curves  and  circles.  These,  so  far  as  I 
could  determine,  represent  the  cut  outlines  of  the  interlobular  and  peri- 
bronchial  tissue  infiltrated  with  cells.  It  has  already  been  stated  that 
these  lines  may  represent  the  paths  along  which  the  swine-plague  bac- 
teria invade  the  lungs  from  the  pleural  surface. 

The  cut  ends  of  the  bronchi  of  the  ventral  lobes  are  frequently  oc- 
cluded with  thick,  whitish  pus ;  in  the  other  lobes  a  reddish  froth  is 
usually  present.  Rarely  they  also  contain  thick  glairy  mucus  in  which 
particles  of  dry  pus  and  lung  worms  are  imbedded.  The  contents  of 
the  air  tubes  in  the  ventral  lobes  may  have  been  derived  from  the  over- 
distended  alveoli,  or  else  a  broncho-pneumonia,  may  have  preceded  the 
swine-plague  pneumonia. 

In  microscopic  sections  of  diseased  lung  tissue  the  alveoli  and  small- 
est air  tubes  are  found  distended  with  cell  masses  consisting  chiefly  of 
leucocytes.  I  have  seen  very  little  fibrin  and  very  few  red  corpuscles  in 
the  alveoli,  even  in  cases  in  which  the  disease  was  quite  recent.  It  may 
be  that  the  stage  represented  in  ordinary  croupous  pneumonia  by  the 
presence  of  fibrin  in  connection  with  the  cellular  elements  is  very  brief, 
and  that  it  is  speedily  replaced  by  large  numbers  of  leucocytes.  The 
large  predominance  of  these  elements  in  some  portions  of  the  lungs,  as 
well  as  beginning  fatty  degeneration,  is  probably  the  cause  of  the  reg- 
ular mottling  of  the  lungs,  as  seen  from  the  surface  and  above  referred 
to.  (See  Plate  ix,  Fig.  2.)  The  little  yellowish  hazy  dots  represent 
the  filled  and  distended  alveoli  surrounded  by  the  hyperaemic  walls. 

The  necrotic  and  caseous  changes  so  frequent  in  swine  plague  deserve 
brief  attention.  The  caseous  changes  were  particularly  noteworthy  iii 
outbreak  IV  (Plates  vn  and  vm,  Fig.  1)  and  necrotic  foci  especially 
abundant  in  outbreak  VII.  (See  Plate  V.)  The  latter  are  usually 
quite  small  and  disseminated  in  large  numbers  over  the  diseased  lobes. 
The  former  represent  larger  masses  from  a  marble  to  a  horse-chestnut 
in  size.  There  is  need  for  a  distinction  between  these  two  forms  of 
necrosis,  as  I  regard  them  as  due  to  different  processes. 

The  necrotic  masses  represent  tissue  which  has  been  destroyed  by 
the  rapid  multiplication  of  swine-plague  bacteria  in  particular  locali- 
ties. Hence  they  are  found  in  all  stages  of  the  pneumonia.  The  large 
caseous  masses  may  be  considered  as  the  result  of  a  slow  death  of 
larger  territories  of  lung  tissue,  due  primarily  to  the  gradual  overdis- 
tensiou  of  the  tissue  by  leucocytes,  and  hence  the  .gradual  cutting  off 
of  the  blood  supply.  One  is  a  rapid  death  due  directly  to  highly  viru- 
lent bacteria,  the  other  a  slow  death,  or  in  other  words  a  kind  of  dry  sup- 
puration in  the  later  stages  of  the  pneumonia,  characteristic  of  the  pig, 
and  due  indirectly  to  the  irritation  of  perhaps  more  attenuated  races 
of  bacteria. 


102 

It  has  already  been  remarked  that  different  species  of  animals  react 
somewhat  differently  to  inflammatory  agents,  and  the  tendency  towards 
caseation  in  the  lungs  of  swine  is,  I  think,  an  illustration  of  the  kind  of 
reaction  manifested  by  swine  as  a  species.  When  irritating  substances 
or  cultures  of  bacteria  are  injected  under  the  skin  of  pigs,  there  is  a 
tendency  to  the  formation  of  a  rather  firm  tumor-like  swelling.  This 
tumor  at  first  consists  of  a  rather  tough,  yellowish-white  mass,  and 
only  after  a  time  softens  in  the  center  into  a  thick,  semi-liquid  pus  re- 
sembling flour  paste.  This  tendency  to  a  firm,  dry  infiltration  of  pus  is 
likewise  observed  in  the  sometimes  quite  extensive  button-like  necroses 
or  "  ulcers"  in  the  large  intestine.  The  same  may  be  said  of  the  large 
homogeneous  cheesy  masses  into  which  the  diseased  lung  tissue  is  con- 
verted after  a  time.  (See  Plate  vn.) 

It  is  not  to  be  understood  from  the  preceding  that  the  pneumonia 
spreads  from  a  single  lobe,  such  as  the  ventral,  in  all  or  most  cases. 
The  case  on  page  69  (No.  385)  is  a  signal  illustration  of  the  contrary.  In 
this  every  lobe  contained  some  necrotic  foci  which  were  evidently  due 
to  a  deposit  of  swine-plague  bacteria  in  these  separate  localities,  and 
which  had  not  yet  coalesced  by  an  extension  of  the  disease  when  the 
animal  succumbed. 

The  inflammation  of  the  pleura  frequently  extends  to  the  pericardium. 
(See  Plate  x.)  This  membrane  is  opaque,  thickened,  and  its  vessels 
distended.  It  may  be  glued  to  the  contiguous  lobes  of  the  lungs  and 
covered  with  exudate.  Less  frequently  it  is  adherent  to  the  surface  of 
the  heart,  which  is  then  covered  by  a  false  membrane,  smooth  or 
roughened,  extending  upon  the  large  vessels  emerging  at  its  base. 

DISEASE  OF   THE  DIGESTIVE  TRACT  IN   SWINE  PLAGUE. 

In  order  to  elucidate  this  important  subject  we  may  briefly  refer  first 
to  the  results  of  inoculation,  second  to  those  cases  of  natural  swine 
plague  from  which  hog-cholera  bacteria  can  be  safely  excluded. 

In  a  considerable  proportion  of  those  animals  which  were  inoculated 
with  swine-plague  cultures  a  severe  catarrhal  inflammation  of  the  lin- 
ing membrane  of  the  stomach  was  produced.  The  hyperaemia  was 
very  intense,  bordering  on  hemorrhage.  Again,  in  another  case  the  ex- 
tension of  the  peritonitis,  produced  by  intra-abdomiual  inoculation, 
along  the  mesentery  caused  a  severe  inflammation  with  exudation  on  the 
mucosa  of  the  small  intestine.  In  one  case  all  Peyer's  patches  of  the 
small  intestine  were  in  a  hypertemic,  partly  heinorrhagic  condition. 

In  outbreak  VIII  there  was  observed  in  3  out  of  5  cases  more  or  less 
extensive  hypersemia  of  the  mucosa  of  the  large  intestine  bordering  on 
a  heinorrhagic  condition.  In  the  case  (No.  385)  caused  by  infection 
from  outbreak  IX,  the  inflammatory  condition  of  the  large  intestine 
was  a  prominent  lesion.  In  these  cases  hog-cholera  bacilli  may  be  ex- 
cluded with  reasonable  certainty.  In  the  earlier  cases  of  outbreak  IV 
a  peculiar  croupous  exudation  appeared,  which  I  have  considered  and 


103 

still  regard  as  the  effect  of  swine-plague  bacteria  in  tbe  large  intestine. 
(See  Plate  vm,  Fig.  2.)  Of  this  lesion  more  or  less  has  been  said  on  page 
24,  in  connection  with  a  brief  review  of  the  outbreak.  It  will  be  remem- 
bered that  in  this  epizootic  hog-cholera  bacilli  were  found  in  the  later 
cases,  while  swine-plague  bacteria  were  present  in  a  large  proportion  of 
both  earlier  and  later  cases.  The  croupous  inflammation  in  this  out- 
break differed  markedly  from  the  necrotic  and  diphtheritic  inflammation 
caused  by  hog  cholera  bacilli.  At  the  same  time  we  must  regard  it  as 
unsatisfactory  in  the  present  state  of  knowledge  to  reason  from  the 
pathology  of  swine  disease  to  its  etiology. 

In  the  remaining  outbreaks  two  classes  appear,  those  in  which  both 
swine  plague  and  hog-cholera  bacilli  were  readily  detected  (II,  V,  VII), 
and  those  in  which  hog-cholera  bacilli  were  not  found,  or  in  which  their 
relation  to  the  disease  was  highly  doubtful  (I,  VI,  IX).  In  most  of 
these  outbreaks  the  intestines  were  diseased,  and  the  lesions  resem- 
bled in  general  those  found  in  hog-cholera  epizootics.  While  there 
can  be  no  reasonable  hesitation  in  attributing  the  intestinal  lesions 
largely  to  hog-cholera  bacilli  when  they  are  detected,  it  is  difficult  to 
understand  those  cases  in  which  hog-cholera  bacilli  are  not  found,  or  in 
which  such  attenuated  forms  are  met  with  occasionally,  the  power  of 
which  to  cause  disease  is  highly  questionable. 

It  is  reasonable  to  assume,  at  least  until  more  knowledge  is  at  hand, 
that,  even  in  those  cases  in  which  bog-cholera  bacilli,  are  not  detected 
in  the  internal  organs  and  yet  extensive  necrosis  and  ulceration  of  the 
large  intestine  is  present,  these  lesions  are  due  to  hog-cholera  bacilli  or 
bacteria  not  yet  recognized.  The  difficulty  of  examining  the  intestines 
for  pathogenic  bacteria  and  the  amount  of  labor  involved  is  very  great, 
and  hence  for  want  of  time  and  sufficient  assistance  this  part  of  the 
work  has  been  set  aside  in  these  investigations  and  the  attention  cen- 
tered on  the  lungs  and  the  other  internal  organs.  It  is  apparent  that 
even  if  certain  bacteria  are  found  in  the  contents  of  the  digestive  tract 
their  relation  to  disease  processes  going  on  there  is  by  no  means  proved, 
since  the  intestines  contain  a  large  variety  of  bacteria  at  all  times.  It 
is  necessary  to  demonstrate  that  with  pure  cultures  of  such  bacteria  the 
same,  or  a  very  similar  intestinal  disease,  can  be  produced.  "While  this 
demonstration  has  frequently  been  made  by  us  with  virulent  hog-cholera 
bacilli,  which  are  also  quite  invariably  present  in  the  spleen,  such  dem- 
onstrations fail  with  swine-plague  bacteria  and  with  very  attenuated 
hog-cholera  bacilli,  and  we  are  at  a  loss  to  determine  how  much  disease- 
producing  power  to  attribute  to  them. 

The  production  of  intestinal  disease  by  swine-plague  bacteria  may  be 
supposed  to  go  on  as  follows :  The  bacteria  first  attack  the  lung  tissue 
and  there  produce  more  or  less  hepatization.  The  blood  finds  its  path 
through  the  lungs  partly  obstructed.  This  reacts  on  the  blood  in  the 
right  side  of  the  heart  and  "the  venous  blood  entering  it.  Hence  there 
may  be  more  or  less  stasis  of  blood  in  the  portal  circulation  which  in 
turn  impairs  the  digestive  functions  of  the  stomach.  The  swine-plague 


104 

bacteria  in  the  lungs  in  the  later  stages  of  the  pneumonia  may  be 
coughed  up  in  the  contents  of  the  bronchial  tubes,  swallowed  and  passed 
through  the  impaired  stomach  unharmed  into  the  intestines.  The  stagna- 
tion of  feces  in  the  large  intestine  furnishes  the  bacteria  an  opportunity 
to  cause  inflammation  of  the  mucous  membrane  and  exudation.  The 
tendency  of  swine-plague  bacteria  to  cause  fibriuous  inflammatory  de- 
posits on  serous  membranes  may  serve  to  explain  such  action  on  mucous 
membranes. 

If  we  continue  to  follow  the  results  of  such  possible  localization  we 
must  assume  that,  in  the  diseased  intestine  a  considerable  multiplication 
of  swine-plague  bacteria  takes  place,  which,  discharged  with  the  feces, 
put  into  the  surroundings  of  the  swine  a  large  number  of  pathogenic  bac- 
teria. These  swallowed  by  healthy  pigs  may  lead  directly  to  intestinal 
disease  without  any  necessarily  extensive  lung  lesions.  The  virus  thus 
multiplied  by  the  multiplication  of  cases  will  produce  a  more  and  more 
virulent  epizootic  in  which  intestinal  lesions  may  predominate.  While 
there  is  no  proof  that  these  phenomena  actually  take  place,  all  the  facts 
observed  in  an  outbreak  readily  accord  with  such  a  hypothesis. 

The  mingling  of  two  diseases,  hog  cholera  and  swine  plague,*  makes 
it  necessary  to  compare  briefly  the  pathogenic  power  of  the  bacteria 
causing  these  diseases.  This  mingling  has  greatly  complicated  our 
understanding  of  the  extent  and  the  kind  of  lesions  attributable  to  each 
bacterium.  Thus,  in  hog  cholera,  the  chief  force  of  the  disease  is  spent 
upon  the  digestive  tract.  The  lungs  are  frequently  involved  in  collapse 
and  broncho-pneumonia  of  limited  extent,  but  collapse  seems  to  be  not 
uncommon  in  apparently  healthy  pigs,  and  broncho-pneumonia  may  be 
conceived  of  as  developing  from  collapse  without  the  necessary  interven- 
tion of  disease  germs.  Again,  the  presence  of  lung  worms  may  account 
for  much  of  the  localized  bronchitis  and  hepatization.  It  is  easy  to 
understand  that  hog-cholera  bacilli  accidentally  present  in  the  blood  in 
disease  may  pass  through  a  healthy  lung  without  injury,  while  lungs 
affected  with  collapse  and  lesions  due  to  lung  worms  may  offer  a  favor- 
able opportunity  for  the  lodgment  of  emboli  containing  bacilli.  The 
disease  process  thus  starting  up  may  be  continued  by  sputum  bacteria 
(resembling  or  identical  with  swine  plague).  It  becomes  difficult  there- 
fore to  determine  whether  hog-cholera  bacilli  have  any  specific  effect 
on  the  lungs. 

In  swine-plague  the  exact  reverse  is  true.  The  predilection  of  swine- 
plague  bacteria  for  the  lungs  is  a  demonstrated  fact  even  with  small 
experimental  animals.  Their  exact  effect  on  the  mucous  membranes  of 
the  caecum  is  not  easily  determinable  owing  to  the  frequent  association 
with  hog  cholera  lesions.  That  they  produce  a^  diffuse  intense  inflam- 
mation, associated  at  times  with  fibrinous  exudation,  will  not,  I  think, 
be  denied  in  view  of  the  facts  brought  out  in  the  experimental  part  of 
this  report. 

*  See  also  p.  138  for  some  practical  observations  on  this  subject. 


105 


"We  have  thus  in  hog  cholera  primary  disease  of  the  intestines  with 
perhaps  secondary  localizations  in  the  lungs;  in  swine  plague  primary 
disease  of  the  lungs  with  secondary  infection  of  the  intestines. 

The  pathological  action  of  these  two  kinds  of  bacteria  can  not  be  for- 
mulated with  any  precision  without  extended  investigations  directed  to 
that  subject  alone.  Meanwhile  a  few  broad  facts  can  be  deduced  from 
the  inoculation  experiments.  Hog-cholera  bacilli  multiply  in  clumps 
in  the  capillaries  of  the  parenchyma  of  the  various  organs,  where  they 
primarily  obstruct  the  circulation,  and  thus  produce  necrosis  of  tissue 
in  their  immediate  vicinity.  When  this  takes  place  in  the  follicular 
apparatus  of  the  intestine  (in  rabbits)  necrosis  of  portions  of  the  mucous 
membrane,  followed  by  ulceration,  may  ensue.  They  do  not  produce 
fibrinous  and  cellular  exudation  on  serous  membranes,  and  probably  do 
not  multiply  on  these  membranes.  Secondarily,  they  produce  paren- 
chymatous  degeneration  of  the  liver,  kidneys,  and  heart  muscle,  which 
degeneration  may  be  due  to  the  toxic  bodies  formed  by  them. 

Swine-plague  bacteria,  on  the  other  hand,  seem  to  .multiply  diffusely 
and  abundantly  wherever  such  multiplication  takes  place.  When  in 
the  blood  death  is  exceedingly  rapid ;  when  in  the  large  serous  cavities, 
exudates  are  quickly  produced  and  death  may  ensue  in  from  3  to  7  days; 
when  under  the  skin  necrosis  and  suppuration  take  place. 

The  following  table  gives  briefly  the  important  differences  observed 
between  hog-cholera  and  swine-plague  bacteria.  Those  features  com- 
mon to  both  are  omitted  : 


SWINE-PLAGUE   BACTERIA. 

Morphological. 

1.  About  I//  long  and  0.5  to 0.6  jj.  wide  in 

(cover-glass  preparations  mounted 
in  balsam). 

2.  They  show  the  so-called  polar  stain 

in  certain  conditions. 

3.  Non-motile. 

Biological. 

4.  Growth  in  bouillon  feeble. 

5.  Growth  on  gelatine  feeble  or  absent. 

6.  Growth  on  potato  fails. 

7.  Tends  to  produce  acid  reaction  of  cul- 

ture liquid. 

8.  Produces  no  fermentation  of  glucose. 

9.  Produces  phenol  and  indol  (f). 

10.  Rapidly  destroyed  in  water,  in  soil, 
by  drying.* 


HOG-CHOLERA  BACILLI. 

Morphological. 

1.  About  1.2  to   1.5  fi  long  and  0.6  n 

wide. 

2.  No  characteristic  polar  stain..    Tile 

central  part  of  rod  frequently  less 
stained  than  periphery. 

3.  Motile  (possess  flagella). 

Biological. 

4.  In  bouillon  moderate. 

5.  On  gelatine  more  vigorous  than  swine 

•plague. 

6.  On  potato  usually  abundant. 

7.  Tends  to  produce  alkaline  reaction. 

8.  Causes  fermentation  of  glucose  with 

production  of  CO2  and  H. 

9.  Produces  neither  phenol  nor  indol. 
10.  Quite  resistant  to  the  same  agents.* 


See  page  92  for  table. 


106 


Pathogenic. 

11.  Multiplies  diffusely  in  blood  or  on 

serous   membranes. 

12.  Produces    septicaemia ;  fibrinons  and 

cellular  inflammation  of  serous 
membranes  and  pneumonia  in  small 
animals. 


13.  Most  virulent  varieties  are  fatal  to 
mice,  rabbits,  guiuea-pigs,  and  pi- 
geons in  very  minute  doses.*  Death 
in  16  to  20  hours. 


Pathogenic. 

11.  Multiplies  in  blood  vessels  in  clumps. 

12.  Does   not    produce    inflammation   of 

serous  membranes.  Produces  pa- 
renchymatous  degeneration  of  vital 
organs.  Necroses  in  liver.  More 
attenuated  varieties  cause  infiltra- 
tion and  ulceration  of  Peyer's 
patches  and  infiltration  of  lymph 
glands. 

13.  Most  virulent  varieties  are  fatal  to 

mice,  rabbits,  and  guiuea-pigs  in 
minute  doses."  Death  in  5  to  8 
days. 


In  view  of  the  mingling  of  these  two  diseases  can  we  by  inoculation 
of  both  bacteria  at  the  same  time  gain  any  information  as  to  their  rela- 
tive activity?  If  both  kinds  of  bacteria  were  of  unchanging  virulence 
this  might  be  done,  but  we  may  have  in  natural  outbreaks  attenuated 
swine  plague  associated  with  virulent  hog-cholera  bacteria  and  the  re- 
verse. Or  one  kind  of  bacteria  may  invade  the  animal  after  the  other 
has  spent  its  energy.  The  variety  of  combinations  which  may  occur  in 
nature  is  too  great  to  be  imitated  by  experiment. 

It  was,  nevertheless,  desirable  to  see  what  effect  the  inoculation  of 
mixed  cultures  might  have.  Hence  the  following  experiment  was  tried, 
the  result  of  which,  though  very  important,  is  not  conclusive. 

May  12,  1891.  Cultures  of  swine  plague  from  outbreak  IX  and  of  hog  cholera  from 
a  Virginia  epizootic,  both  the  most  virulent  in  the  laboratory,  were  chosen.  From 
the  growth  on  an  agar  culture  of  these  swine-plague  bacteria  24  hours  old  a  turbid 
suspension  iu  bouillon  was  prepared.  A  bouillon  culture  of  the  hog-cholera  bacilli 
only  24  hours  old  in  which  the  growth  was  abundant  was  also  on  hand.  With  these 
cultures  three  pigs,  about  6£  months  old,  of  the  same  breed  and  lot,  wore  inoculated 
as  follows : 

No.  462  received  into  the  right  lung  one-fourth  cubic  centimetre  of  the  swine- 
plague  suspension,  and  three-fourths  cubic  centimetre  of  the  hog-cholera  bouillon 
mixed. 

No.  463,  inoculated  in  the  same  way  with  twice  this  quantity,  i.  e.,  one-half  cubic 
centimetre  swine-plague  and  1£  cubic  centimetre  hog-cholera  culture. 

No.  461  received  5  cubic  centimetres  of  the  hog-cholera  culture  alone  into  the  right 
lung. 

No.  463  was  dead  next  morning,  within  16  hours  after  inoculation.  Animal  in  good 
condition;  weight  72  pounds.  Subcutaneous  fat  reddened.  Blood  oozes  from  the 
cut  vessels  and  coagulates  feebly.  Arborescent  injection  of  minute  bloodvessels 
of  connective  tissue  in  axilla  and  between  muscles  on  thorax.  In  abdominal  cavity 
a  considerable  quantity  of  yellowish  serum.  Ventral  portion  of  spleen  imbedded 
in  an  elastic  whitish  exudate.  Costal  and  diaphragmatic  pleura  show  intense 
vascular  injection.  In  right  pleural  sac  about  140  cubic  centimetres  blood-stained 

*  It  must  be  borne  in  mind  that  the  various  attenuations  of  hog-cholera  and  swine- 
plague  bacteria  can  not  be  individually  considered  with  reference  to  their  pathogenic 
effect  in  a  tabulated  form ;  we  must  refer  to  the  text  for  these.  . 


107 

liquid,  in  left  70  cubic  centimetres.  Lungs  but  partly  collapsed  :  oedematous.  Over 
the  entire  right  lung  a  very  thin  friable  oxudate;  over  the  left  this  is  found  only 
on  most  dependent  portion.  Right  lung  punctured  by  needle  in  principal  lobe.  The 
puncture  shows  as  a  hemorrhagic  spot. 

In  the  stomach— which  is  tilled  with  food — and  in  intestines,  nothing  abnormal. 
Kidneys  with  base  of  pyramids  dark  red.  Spleen  slightly  enlarged. 

In  the  spleen  pulp  only  swine-plague  bacteria  detected.  In  an  agar  culture  there- 
from no  motile  bacilli  seen.  A  bouillon  culture  from  the  peritoneal  exudate  contains 
only  swine-plague  bacteria.  Cover-glass  preparations  from  both  pleural  and  perito- 
neal exudate  show  numerous  polar  stained  bacteria. 

No.  4(52  manifested  labored  breathing  soon  after  the  inoculation.  It  lay  on  its 
bedding  unable  to  get  up.  It  was  found  dead  May  16. 

Considerable  reddening  of  the  skin  on  ventral  aspect  of  body.  Subcutis  as  in  463. 
In  abdominal  cavity  a  small  quantity  of  yellowish  serum  and  somenbrinous  coagula. 
Spleen  quite  large,  congested  and  friable. 

Thoracic  cavity.  Eight  pleural  sac  contains  100  cubic  centimetres  of  turbid  dark 
red  fluid.  Considerable  friable  exudate  covering  costal  and  pulmonary  pleura  of  this 
side,  especially  abundant  on  small  lobes.  Pleura  opaque,  thickened  and  wrinkled. 
Both  cephalic  and  ventral  lobes  not  enlarged,  but  firm,  on  section  grayish  red,  solid. 
Bronchioles  filled  with  whitish  muco-pus.  The  needle  puncture  in  principal  lobe  is 
the  center  of  a  hepatized  mass,  fully  2  inches  in  diameter;  on  section  some  lobules 
bright  red,  others  hemorrhagic,  dark  red.  Nearer  periphery  of  this  mass  the  hepa- 
tization  is  grayish  red ;  the  interlobular  and.  peribrouchial  tissue  appear  as  irregular 
grayish  lines.  In  the  left  lung  the  principal  lobe  congested;  slight  interlobular 
oedema.  Along  cephalic  border,  under  pleura,  a  dark  red  hepatized  mass,  about  one- 
half  inch  in  diameter.  Tip  of  ventral  lobe  adherent  to  pericardium,  beneath  adhe- 
sions small  foci  of  dark  red  hepatizatiou.  In  terminal  bronchi  adult  lung  worms. 

Pericardium  adheres  to  heart  surface  by  means  of  a  thick  yellowish  pseudo-inem- 
brane.  Glands  along  posterior  aorta  hemorrhagic. 

Digestive  tract :  Stomach^empty.  Mucosa  thrown  into  folds  and  covered  with  an 
abundance  of  very  viscid  mucus.  In  fundus  it  is  congested.  Hyperoemia  also  around 
cardiac  expansion.  Duodenum  pigmented.  Mucosa  of  ileum  swollen  and  sprinkled 
with  small  hemorrhagic  spots.  Mucosa  of  caecum  and  upper  colon  discolored.  In 
lower  colon  minute  whitish  spots,  with  injected  margin,  evidently  superficial  ulcers. 
Meso-colic  glands  enlarged,  hypera3mic. 

Liver  somewhat  enlarged,  quite  firm.  Acini  slightly  projecting;  some  dark  red; 
in  most  of  them  iutralobular  necrotic  masses,  the  result  of  some  former  disease.* 
Portal  glands  enlarged  and  hypertemic.  Kidneys  congested;  pyramids  dark  bluish 
red.  Glomeruli  just  visible  to  naked  eye  as  injected  points. 

Bacteriological  examination  :  In  cover-glass  preparations  from  the  hepatized  mass 
of  right  principal  lobe  very  many  swine-plague  bacteria  and  a  few  somewhat  larger 
forms.  In  two  agar  plates  from  the  same  region  large  number  of  colonies  of  two  kinds 
appear.  One  represents  swine-plague  about  ten  times  more  numerous  than  the  hog- 
cholera  colonies,  which  are  on  second  day  twice  as  large.  In  cover-glass  prepara- 
tions of  spleen  pulp  a  considerable  number  of  bacteria  appearing  as  hog-cholera 
bacilli.  The  same  is  true  of  the  liver.  Agar  plates  from  each  organ  contain  only 
colonies  of  hog-cholera  bacilli. 

No.  461,  though  sick  for  a  few  days,  fully  recovered. 

This  experiment  illustrates  the  greater  rapidity  of  action  of  swine- 
plague  bacteria  even  in  small  doses.  It  also  demonstrates  their  greater 
virulence,  for  the  pig  inoculated  with  a  large  dose  of  hog-cholera  bacilli 

*  This  condition  of  the  liver  will  be  discussed  in  a  subsequent  publication.  It  bears 
no  relation  to  the  inoculation,  since  it  is  found  in  swine  otherwise  healthy. 


108 

alone,  although  sick  for  a  few  days,  recovered.  Another  fact  of  im- 
portance illustrated  in  these  cases  is  the  slow  action  of  hog-cholera 
bacilli  in  invading  other  organs.  Thus  the  swine-plague  bacteria  had 
killed  No.  463  before  the  hog-cholera  bacilli  had  invaded  the  spleen 
and  liver.  In  No.  462,  however,  enough  time  had  elapsed  to  permit  the 
hog-cholera  bacilli  to  spread  through  the  body  while  the  swine-plague 
bacteria  were  now  limited  to  the  lungs.  The  invasive  power  of  hog- 
cholera  bacilli,  though  slower,  is  nevertheless  more  lasting. 

There  is  no  evidence  to  support  the  view  that  either  swine-plague  or 
hog-cholera  bacilli  may  produce  serious  disease  in  man.  No  bacteria 
have  thus  far  been  described  as  the  cause  of  human  disease  which  are 
identical  with  either  of  the  bacteria  of  swine  disease.  Nevertheless 
the  possibility  of  an  occasional  transmission  from  animal  to  man  can  not 
be  wholly  set  aside  until  more  thorough  bacteriological  investigations 
of  human  diseases  shall  have  been  made  in  those  localities  where  infec- 
tious swine  diseases  are  very  prevalent. 

It  is  of  interest  to  note  that  among  human  diseases  typhoid  fever 
bears  a  close  resemblance  to  hog  cholera,  not  only  as  regards  the  gen- 
eral character  of  the  specific  bacteria,  but  also  with  reference  to  the 
disease  itself.  Again  the  diplococcus  of  croupous  pneumonia  in  man 
has  many  points  of  likeness  with  swine-plague  bacteria.  The  general 
pathological  effect  as  well  as  the  tendency  to  produce  various  forms  of 
disease  by  localizations,  such  as  pleuritis,  pericarditis,  meningitis,  are 
strikingly  similar  to  the  miscellaneous  lesions  caused  by  swine  plague 
bacteria.  Typhoid  fever  and  pneumonia  are  notinfrequently  associated 
in  man,  thus  affording  another  point  of  similarity  to  the  frequently  asso-- 
ciated  swine  diseases.  Another  peculiarity  which  is  common  to  the 
pneumonia  bacteria  in  man  and  to  those  of  swine-plague  is  their  frequent 
occurrence  in  the  mouth  and  upper  air-passages  of  man  on  the  one  hand, 
of  swine  on  the  other.* 

*  See  the  following  chapter  and  appendix. 


ATTENUATED  SWINE-PLAGUE  BACTERIA  IN  SPORADIC  CASES  OF  PNEUMONIA  AND 

IN  SEPTIC  DISEASES  OF  SWINE,  AND  IN  THE  UPPER  AIR  PASSAGES  OF 

HEALTHY  SWINE  AND  OTHER  DOMESTICATED  ANIMALS.* 

During  the  investigations  of  the  epizootic  forms  of  swine  plague 
described  in  these  pages,  bacteria  not  distinguishable  from  those  of 
this  disease  were  occasionally  encountered  in  sporadic  cases  of  pneu- 
monia. The  affected  swine  were  usually  those  which  had  been  exposed 
to  hog  cholera  or  swine  plague,  or  mixed  outbreaks,  or  had  been  inocu- 
lated and  had  survived.  They  were  kept  isolated  for  a  time  by  them- 
selves or  with  other  cases  of  similar  history,  and  they  generally  died  after 
some  months  or  became  so  unthrifty  that  they  were  killed.  Occasion- 
ally they  died  with  some  inflammation  of  the  serous  membranes,  such 
as  peritonitis,  pericarditis,  or  pleuritis.  In  such  cases  when  examined 
swine  plague  bacteria  were  as  a  rule  detected.  These  lesions  were 
attributed  to  injuries  which  the  swine^ penned  together,  inflicted  upon 
one  another  by  fighting.  If  we  bear  in  mind  the  variety  of  lesions 
which  may  be  produced  by  swine  plague  bacteria  when  inoculated  into 
healthy  swine  (pneumonia,  pleuritis,  pericarditis,  peritonitis,  inflamma- 
tion, and  suppuration  of  the  joints,  inflammation  with  exudation  in  the 
intestines),  we  need  not  be  surprised  to  encounter  them  in  similar 
affections  arising  under  the  usual  conditions. 

The  sporadic  cases  of  pneumonia  were  puzzling  in  so  far  as  it  was 
difficult  to  account  for  the  presence  of  swine-plague  bacteria.  These, 
as  we  have  shown,  very  easily  perish  by  drying,  and  when  in  water  and 
in  media  unsuitable  for  their  development.  How  they  can  survive  for 
weeks  and  months  in  the  surroundings  of  swine  is  inexplicable.  To 
find  some  other  explanation  I  was  led  to  examine  the  respiratory  tract 
of  apparently  healthy  pigs  to  see  if  here,  in  a  manner  analogous  to 
the  bacteria  of  pneumonia  in  man,  they  survived  and  became  a  poten- 
tial source  of  infection  under  certain  conditions.  The  result  was  posi- 
tive in  many  cases.  Swine-plague  bacteria  or  bacteria  not  distinguish- 
able from  them  were  found  in  the  nose,  at  the  base  of  the  tongue  and  in, 
the  larynx  of  a  certain  number  of  healthy  swine. 

*  In  this  chapter  no  effort  has  been  made  to  give  an  historical  review  of  those 
experiments  made  by  former  observers  which  demonstrated  the  occasional  virulence 
of  the  saliva  of  mail  and  animals.  The  general  relationship  of  these  bacteria  from 
various  domesticated  animals  to  swine  plague  bacteria  is,  1  thiuk,  brought  out  for 
the  first  time  in  these  pages.  See  also  appendix  to  this  report. 

100 


110 

The  cases  which  have  come  under  our  observation  may  be  grouped 
into  several  classes : 

1.  Sporadic  pneumonia. 

2.  Other  affections,  chiefly  inflammations  of  serous  membranes. 

3.  Older  animals  having  passed  through  diseases  but  apparently 
healthy. 

4.  Younger  animals  not  known  to  have  been  exposed  to  disease. 

5.  Animals  entirely  free  from  these  bacteria. 

Groups  1,  2,  and  3  generally  include,  in  our  observations,  older  ani- 
mals. 

The  method  used  in  all  cases  was  the  subcutaneous  inoculation  of 
rabbits  with  the  tissue,  secretion,  or  exudate  suspected  of  carrying  these 
bacteria.  The  inoculations  were  made  in  part  conjointly  with  Veterina- 
rian F.  L.  Kil borne;  in  part  by  him  alone.  Great  care  was  taken  to 
prevent  infection  from  external  sources.  At  first  only  the  nasal  secre- 
tion was  used.  This  was  drawn  up  with  a  sterile  pipette  and  then  in- 
troduced into  the  subcutis  of  the  rabbit  through  a  small  incision  in 
the  skin.  This  method  did  not  seem  quite  satisfactory,  and  in  a  num- 
ber of  cases  the  animal  was  killed  by  bleeding,  the  mouth  carefully 
exposed  from  below  and  mucus  collected  from  the  base  of  the  tongue, 
the  posterior  nares,  epiglottis,  and  from  beneath  the  vocal  cords.  The 
mucus  was  placed  in  a  sterile  watch  glass.  The  skin  of  the  rabbit  was 
freed  from  hair  and  thoroughly  washed  with  a  solution  of  mercuric 
chloride  1:500;  with  flamed  scissors,  the  skin  was  cut  through  usually 
on  the  side  of  the  abdomen,  a  little  pocket  formed,  and  a  drop  of  mu- 
cus put  into  it  with  flamed  forceps.  The  incision  was  either  left  to 
itself  or  united  with  a  stitch  of  sterilized  silk. 

These  precautions  thus  prevented  any  external  infection.  At  the 
same  time  a  prolonged  experience  in  such  work  leads  me  to  believe  that 
swine-plague  bacteria  are  not  transmitted  in  a  dried  condition,  excepting, 
perhaps,  for  a  few  days  only.  The  outcome  of  the  inoculations  also  in- 
clined us  to  exclude  any  accidental  infection.  When  several  rabbits 
were  inoculated  with  mucus  from  the  same  locality  they  either  died 
together  or  both  survived. 

The  demonstration  of  swine-plague  bacteria  in  the  upper  air  passages 
of  swine  naturally  led  to  an  examination  of  the  air  passages  of  other 
domesticated  animals  by  the  same  methods.  These  are  reported  by 
Dr.  V.  A.  Moore,  assistant  in  the  laboratory,  to  whom  this  part  of  the 
work  was  intrusted.  It  will  be  seen  from  this  report  that  an  attenuated 
variety  of  bacteria,  belonging  to  the  group  of  swine-plague  bacteria  and 
not  distinguishable  from  them,  inhabit  the  mouth  and  upper  air  passages 
of  such  domesticated  animals  as  cattle,  dogs,  and  cats,  and  that  some 
sporadic  diseases  among  smaller  animals,  such  as  rabbits,  guiuea-pigs, 
and  fowls,  are  caused  by  the  same  bacteria.  This  group  has  a  wide 
distribution,  therefore,  and  may  be  regarded  as  a  more  or  less  common 
inhabitant  of  the  mucous  membranes. 


Ill 

In  the  following  brief  synopsis  of  the  cases  illustrative  of  the  above 
statements,  they  are  grouped  as  nearly  as  possible  in  accordance  with 
the  classification  above  outlined: 

1.  Sporadic  pneumonia. — Pig  No.  481.  Placed  in  infected  hog-cholera  pen  January 
11,  1888.  Since  February  1,  large  sores  are  observed  on  the  shoulders,  attributed  to 
bites  inflicted  by  other  swine  in  the  pen.  It  died  March  5,  very  much  emaciated. 
In  the  caecum  several  crater-like  ulcerations,  involving  the  muscular  coats.  In  the 
upper  colon  about  a  dozen  ulcers,  one-fourth  to  three-eighths  inch  in  diameter. 

The  ventral  and  cephalic  lobes  of  both  lungs  and  the  roots  of  principal  lobes,  also 
foci  in  median  lobe,  hepatized,  pale  red. 

A  bit  of  diseased  lung  tissue  toru  up  in  sterile  bouillon  and  one-fourth  cubic  centi- 
metre injected  into  a  rabbit.  It  died  in  40  hours,  with  exudative  peritonitis,  due  to 
swine-plague  bacteria. 

In  this  case  these  bacteria  may  have  come  from  the  other  animals  in  the  infected 
pen.  In  the  following  case  the  source  is  not  so  obvious. 

No.  492,  received  at  the  Station  January  25,  1888,  with  three  others  (490-493,  in- 
clusive). In  making  inoculations  from  the  nasal  mucus  of  these  pigs,  to  be  described 
later,  Dr.  Kilborne  noticed  that  the  secretion  was  muco-purulent,  while  in  other  pigs 
handled  at  the  same  time  it  was  serous.  No.  492  became  unthrifty,  and  died  about  a 
month  after  it  was  brought  to  the  Station. 

The  lungs  were  firmly  bound  to  diaphragm  and  chest  wall  by  old  adhesions.  The 
ventral  and  cephalic  lobes,  the  roots  of  the  principal  lobes  of  both  lungs  and  the  me- 
dian Jobe  airless,  in  condition  of  broncho-pneumonia.  The  catarrhal  masses  in 
the  alveoli  appeared  as  a  pale  grayish  yellow,  delicate  mottling  under  the  pleura. 
Throughout  the  hepatized  portions  are  yellowish  necrotic  foci  one-sixteenth  to  one- 
eighth  inch  in  diameter.  The  smaller  bronchi  contain  a  soft,  creamy  muco-pus.  In 
the  large  bronchi,  the  mucosa  hyperiemic.  Bronchial  glands  enlarged,  very  pale 
and  firm. 

Two  rabbits  inoculated  as  in  prece  ding  case.  One  died  in  40  hours,  the  other  on 
the  third  day.  Bacteria  showing  the  polar  stain  present  in  large  numbers  in  organs 
of  the  first ;  in  small  numbers  in  the  second  rabbit,  In  cultures  they  are  not  distin- 
guishable from  swine-plague  bacteria. 

Pig  No.  267,  received  October  16,  1889.  This  animal  belonged  to  a  lot  of  swine 
which  had  been  inoculated  with  attenuated  hog-cholera  cultures  and  subsequently 
exposed  to  hog  cholera.  The  animal  died  January  2,  1890.  In  the  lungs  were  regions 
of  collapse  and  broncho-pneumonia,  as  well  as  marked  bronchitis.  From  the  abun- 
dant mucus  in  the  upper  trachea  two  rabbits  were  inoculated.  They  succumbed  on 
the  fourth  and  the  sixth  days,  respectively,  to  an  exudative  and  hemorrhagic  peritoni- 
tis characterized  by  the  presence  of  swine-plague  bacteria. 

Pig  No.  188.  This  animal  was  placed  in  an  infected  hog-cholera  pen  March  13, 1889, 
and  removed  in  5  days.  It  was  killed  December  9,  after  a  long  period  of  unthrifti- 
ness.  The  ventral  lobes  of  both  lungs  were  hepatized,  of  a  grayish-red  appearance 
(broncho-pneumonia).  The  liver  covered  with  bluish  and  whitish  patches,  in  which 
the  interlobular  tissue  is  thickened.  This  thickening  is  limited  to  the  surface.  One 
rabbit  inoculated  with  mucus  from  larynx  died  in  10  days,  with  extensive  subcutane- 
ous purulent  infiltration  and  exudative  peritonitis.  The  only  bacteria  found  were 
the  swine-plague  bacteria. 

Pig  No.  308  was  purchased  from  a  neighboring  farm  February  7.  Four  days  later 
it  was  killed  and  hepatization  of  a  portion  of  both  prinicipal  lobes  determined,  to- 
gether with  bronchitis  of  the  air  tubes  leading  to  these  diseased  regions.  Two  rab- 
bits were  inoculated  from  the  tracheal  and  pharyngeal  mucus,  and  one  from  the 
hepatized  lung.  The  latter  remained  alive,  while  the  two  former  died  in  3  and  4  days, 
respectively,  with  extensive  exudative  peritonitis.  The  swine  plague  bacteria  alone 
were  present  in  the  organs  of  both  rabbits. 


112 

Pig  No.  119  was  placed  in  an  infected  hog-cholera  pen  January  22,  1889,  where  tho 
swine-plague  disease  was  present.  September  2  it  was  transferred  to  another  pen, 
and  killed  January  13,  1890.  The  internal  organs  were  healthy,  with  the  exception 
of  the  lungs,  in  which  there  were  several  small  foci  of  collapse  and  some  lung  worms. 
One  rabbit  inoculated  with  nasal  mucus  from  the  base  of  the  tongue  died  in  3  days. 
There  was  considerable  phlegmonous  inflammation  and  peritonitis  as  the  result  of  the 
inoculation.  The  peritoneal  exudate  contained  immense  numbers  of  swine-plague 
germs.  The  other  rabbit  inoculated  with  mucus  from  below  the  vocal  chords  died  in 
3  days  with  the  same  lesions  and  bacteria  present. 

2.  Other  affections. — Pig  No.  180.  This  pig  was  exposed  to  hog  cholera  in  an  infected 
pen  March  13,  removed  March  18.  It  survived  the  exposure  and  was  killed  June  4. 
Its  internal  organs  were  normal  with  exception  of  the  peritoneal  cavity,  which  con- 
tained a  considerable  quantity  of  cloudy  serum,  the  result  of  peritonitis.  Four 
rabbits  were  inoculated  from  mucus  obtained  from  below  the  vocal  chords  and  at  the 
base  of  the  tongue.  The  two  inoculated  from  tho  latter  source  died  in  about  24 
hours.  In  both  the  spleen  and  blood  contained  largo  numbers  of  swine-plague  bac- 
teria. The  two  inoculated  with  tracheal  mucus  died  within  36  hours.  The  spleen  of 
both  contained  large  numbers  of  the  swine-plague  bacteria. 

Pig  No.  202.  This  animal  was  fed  in  May,  1889,  with  small  quantities  of  culture 
liquid  containing  hog-cholera  bacilli  twice  a  day  for  a  week  without  producing  a 
fatal  disease.  November  15  it  was  penned  with  No.  119,  which  harbored  the  swine- 
plague  germs.  February  14  it  was  killed  by  bleeding,  and  two  rabbits  inoculated 
with  mucus  from  the  base  of  the  tongue  and  from  the  larynx  respectively.  Both 
rabbits  died,  one  in  3,  the  other  in  4  days.  The  lesions  consisted  in  subcutaneous  in- 
flammation and  exudative,  partly  hemorrhagic  peritonitis.  Swine-plague  germs 
were  present  in  the  various  organs,  especially  in  the  peritoneal  exudate. 

No.  37.  This  animal  had  been  inoculated  in  the  lungs  with  a  culture  of  swine- 
plague  bacteria,  October  8,  1888.  January  27,  1889,  it  was  exposed  to  hog'cholera, 
which  exposure  it  survived.  It  was  killed  August  16,  in  a  very  good  condition.  The 
only  noticeable  abnormal  condition  was  the  firm  adhesion  of  the  right  lung  to  the 
chest  wall  by  means  of  firm,  fibrous  tissue,  the  result  of  the  swine-plague  inoculation. 
The  lungs  themselves  healthy.  Three  rabbits  were  inoculated  with  mucus  from  the 
respiratory  passages  (tongue,  nose,  and  larynx).  All  three  rabbits  died,  two  in  48 
hours,  the  third  in  4  days.  In  the  latter  the  inflammation  at  the  place  of  inoculation 
and  the  peritonitis  were  most  pronounced.  In  the  organs  of  all  three  rabbits  the 
swine- plague  bacteria  were  present,  especially  numerous  in  the  peritoneal  exudate. 

The  following  case  is  of  importance,  because  the  bacteria  obtained 
from  it  were  tested  upon  pigs  and  found  virulent. 

No.  164  survived  a  hog-cholera  exposure  early  in  1886,  and  in  June  of  the  same  year 
was  transferred  to  another  pen.  It  was  kept  until  October,  1887,  at  which  time  it 
died  of  peritonitis,  probably  occasioned  by  injuries  received  in  fighting  with  other 
pigs  in  the  same  pen.  No  bacteriological  examination  was  made  of  the  peritoneal 
exudate,  but  two  rabbits  were  inoculated  with  mucus  from  the  trachea. 

One  died  in  20  hours ;  in  the  various  organs  numerous  bacteria  showing  polar  stain. 
The  other  died  on  second  day,  with  the  same  bacteria,  as  demonstrated  by  the  micro- 
scope and  cultures  in  bouillon  and  gelatine. 

To  test  farther  the  relative  virulence  of  these  bacteria  a  peptone  bouillon  culture 
was  prepared,  of  which  two  mice  received  subcutaneously  one-twelfth  cubic  centi- 
metre ;  two  pigeons  received  subcutaneously  and  into  the  muscular  tissue  one-fourth 
cubic  centimetre  ;  one  guinea-pig  received  subcutaneously  one-eighth  cubic  centime- 
tre, and  one  rabbit  one-twelfth  cubic  centimetre. 

The  guinea-pig  and  the  pigeons  remained  well.  One  mouse  died  in  24  hours,  the 
other  in  3  days.  In  the  first  large  numbers  of  bacteria;  in  the  second  few.  The 
rabbit  died  within  2  days.  In  this  animal  there  was  slight  infiltration  of  skin  and 


113 

subcutis  at  point  of  inoculation.  Peritonitis.  Invagination  of  lower  colon.  In  the 
various  organs  and  peritoneal  exudate  numerous  bacteria  showing  polar  stain. 

The  pathogenic  character  of  these  bacteria  was  further  demonstrated  by  inocu- 
lation of  swine. 

November  11,  1887.  No.  431,  6  weeks  old,  received  into  right  lung  through  chest 
wall  2-J-  cubic  centimetres  of  a  peptone  bouillon  culture. 

No.  432,  6  weeks  old,  received  the  same. 

No.  433,  6  weeks  old,  received  5  cubic  centimetres  subcutaneously. 

No.  433,  though  affected  by  the  inoculation  for  a  time,  recovered. 

No.  431  appeared  paralyzed  and  unable  to  get  up  3  or  4  days  after  the  injection, 
Respirations  somewhat  quickened.  It  took  very  little  food.  Found  dead  14  days  after 
inoculation. 

Slight  infiltration  in  subcutis  at  point  of  injection.  Right  lung  collapsed.  Pleu- 
ral  cavity  half  full  of  blood-stained  serum.  Considerable  spongy,  yellowish  exudate 
is  loosely  attached  to  the  walls  of  the  Thorax,  the  lung  surface,  and  the  diaphragm. 
The  lung  tissue  is  not  hepatized  excepting  a  small  mass  which  is  necrosed  and  which 
probably  represents  the  place  where  the  needle  penetrated.  Left  lung  not  affected, 
closely  bound  to  thorax  by  fibrous  adhesions  which  give  way  without  much  diffi- 
culty. The  lymph  gland  near  root  of  neck  very  large,  whitish  on  section,  small  yel- 
lowish foci  in  cortex  and  medulla.  Slight  fibrinous  exndate  and  considerable  yellow 
serum  in  abdomen.  In  upper  and  middle  portion  of  colon,  the  mucosa  is  covered  by 
patches  of  a  very  thin  grayish  deposit,  suggesting  necrosis  of  the  surface  epithelium. 

Cultures  from  spleen  negative;  those  from  pleural  exudate  show  the  injected  bac- 
teria only.  A  rabbit  inoculated  subcutaneously  with  about  one  drop  of  serum  from 
the  pleural  cavity  diluted  in  sterile  beef  infusion  died  within  48  hours.  No  local  re- 
action or  peritonitis.  Innumerable  polar-stained  bacteria  in  the  spleen,  which  is 
enlarged,  friable.  Fewer  in  the  liver;  still  fewer  in  blood  from  heart.  Cultures  re- 
vealed the  same  organism. 

No.  432  breathed  with  difficulty  for  several  days  after  the  injection.  It  seemed 
feverish  and  refused  food.  Within  two  weeks  it  was  greatly  improved.  December  27 
its  rectum  was  prolapsed  and  it  died  a  week  later.  At  the  autopsy  the  cause  of  death 
was  found  to  be  invagination  and  rupture  of  ileum.  The  lungs  presented  some  inter- 
esting features.  The  right  lung  was  adherent  to  thoracic  walls  and  diaphragm  by 
means  of  fibrous  tissue  not  yet  very  firm.  The  left  lung  was  adherent  in  several 
places.  The  various  lobes  of  the  right  lung  were  bound  together  by  fibrous  tissue 
and  to  a  tumor  lying  between  principal  and  ventral  lobe  along  ventral  border  of  Inng. 
The  tumor  was  removed  by  careful  dissection,  the  lung  tissue  being  slightly  con- 
densed and  hyperaemic  near  attachment.  There  was  no  hepatization  of  either  lung. 
The  tumor  felt  tense,  walls  about  one-eighth  inch  thick,  inside  dark  red.  Contents 
putty-like,  grayish,,  made  up  of  pus.  Pericardium  thickened  and  attached  in  several 
places  to  epicardium,  which  is  likewise  thickened,  opaque. 

In  a  gelatine-roll  culture  inoculated  with  a  particle  of  the  dry  pus  numerous  col- 
onies of  the  injected  bacteria  appeared  after  a  week.  A  rabbit  inoculated  with  a 
particle  of  pus  died  in  5  days  with  considerable  local  infiltration  and  enlarged  spleen. 
No  peritonitis.  In  the  spleen  a  moderate  number  of  bacteria  identified  in  cultures 
with  those  originally  injected  into  the  pig. 

These  bacteria  were  in  every  way  like  the  various  swine-plague  bac- 
teria with  one  exception.  In  liquid  cultures  when  one  or  two  days  old, 
translucent  capsules  could  be  seen  surrounding  the  bacteria  individu- 
ally when  the  liquid  was  examined  in  the  hanging  drop  and  the  border 
of  the  drop  was  carefully  scrutinized.  This  method  I  have  found  of  much 
service  in  disclosing  the  presence  of  these  glassy  envelopes  when  dry- 
ing and  staining  failed  to  bring  them  into  view.  The  bacteria,  as  they 
1614 8 


114 


are  drawn  to  the  border  of  the  drop,  do  not  touch  one  another,  but  re- 
main separated  from  each  other  by  a  space  of  definite  width.  Careful 
focussing  then  will  also  bring  out  the  very  faint  outlines  of  the  oval 
transparent  capsules.  In  the  inoculations  above  described,  the  capsules 
served  as  an  important  means  of  identifying  these  swine-plague  bacteria 
from  case  to  case. 

3.  Older  animals  apparently  healthy  but  previously  exposed  to  disease. — 
Under  this  head  would  come  some  of  the  cases  already  recorded  and 
the  following : 

No.  420  Lad  been  inoculated  with  hog-cholera  bacilli  October  6,  1887,.  and  with 
swine-plague  bacteria  October  20.  March  1,  1888,  a  drop  of  mucus  taken  from  nares 
with  a  capillary  pipette  and  forced  into  subcutis  of  a  rabbit  through  a  skin  incision. 
The  rabbit  died  in  10  days  with  exudative  pleuritis.  the  exudate  containing  swine- 
plague  bacteria. 

No.  219.  This  animal  was  inoculated  subcutaneously  with  attenuated  hog-cholera 
cultures  September  27, 1889.  It  was  killed  January  13, 1890,  and  found  normal.  There 
was  at  the  place  of  inoculation  an  encysted  caseous  mass  about  1  inch  in  diameter. 
Three  rabbits  were  inoculated  with  mucus  from  the  respiratory  tract.  Of  these  but 
one  rabbit  died  on  the  llth  day  with  purulent  pleuritis  and  pericaraitis.  Swine- 
plague  bacteria  were  obtained  from  the  exudate  and  their  virulence  tested  by  inocu- 
lating a  fresh  rabbit  with  a  pure  culture. 

4.  Animals  not  known  to  have  been  exposed  to  disease. 

October  6.  Nasal  mucus  obtained  from  the  nares  of  a  healthy  pig  on  a  flamed  glass 
rod  is  stirred  up  in  sterile  water  and  one-half  cubic  centimetre  injected  subcutane- 
ously into  two  rabbits. 

No.  1.  Dead  October  12.  Purulent  thickening  of  the  subcutis  at  point  of  inocula- 
tion and  extending  thence  over  abdomen  and  thorax  as  a  sanguinoleut  effusion.  Per- 
itoneum roughened.  A  cover-glass  placed  on  csecum,  removed  and  stained,  shows 
immense  numbers  of  bacteria  exhibiting  the  polar  staiu.  The  same  bacteria  scarce 
in  blood,  spleen  and  liver. 

No.  2.  Dead  October  13.  Lesions  as  in  No.  1.  Exudative  peritonitis  with  ecchy- 
moses  on  caecum. 

Cultures  from  both  cases  on  gelatine  and  in  bouillon  contain  only  swine-plague 
bacteria. 

Additional  inoculations  were  made  February  2  and  March  1,  1888. 
Nasal  mucus  from  supposedly  healthy  pigs  was  collected  in  a  capillary 
pipette  and  a  drop  forced  with  a  rubber  bulb  into  a  subcutaneous  pocket 
made  by  an  incision  through  the  skin.  The  incision  was  closed  with 
collodion. 


Date. 

Rabbit 
No. 

From 
pig  No. 

Result. 

Feb.     2 

1 

483 

Negative. 

Feb.     2 

2 

484 

Do. 

Feb.     2 

3 

493 

Dies  in  48  hours.    Large  numbers  of  polar-stained  bacteria  in 
blood,  spleen  and  liver. 

Feb.     2 

4 

491 

Negative. 

Mar.    1 

5 

490 

Do. 

Mar.    1 

6 

491 

Dies  in  7  days.   Extensive  purulent  infiltration  of  snbcutis;  cul- 

tures negative. 

Mar.    1 

7 

493 

Negative. 

Mar.    1 

8 

483 

Do. 

Mar.    1 
Mar.    1 

9 
10 

482 
484 

Dies  in  13  da3'8.    Pneumonia  and  exudative  plenritis. 
Dies  in  7  days.    Same  as  No.  6.    Bacteria  obtained  from  spleon 

in  cultures  fatal  to  a  rabbit  in  48  hours. 

Mar.    1 

11 

468 

Dies  in  13  days.    Same  as  No.  9. 

115 

No.  468  belonged  to  one  lot  brought  to  Station  January  4,  1888. 

Nos.  490  to  493,  inclusive,  to  another  lot  brought  to  Station  January 
25,  1888. 

Nos.  481  to  484,  inclusive,  to  still  another  lot  brought  to  Station  Janu- 
ary 10,  1888. 

The  inoculation  disease  in  the  rabbits  varied  considerably.  In  one,  death  ensued  in 
48  hours.  Nos.  6  and  10  died  in  7  days,  and  in  both  there  was  extensive  purulent  in- 
filtration of  subcutis  over  abdomen  and  thorax.  Finally,  in  Nos.  9  and  11  there  was 
exudative  pleuritis  with  pneumonia.  In  No.  9,  one-half,  in  No.  11,  the  whole  of  the 
left  lung  hepatized.  In  the  pleuritic  exudate  and  the  lung  tissue  large  numbers  of 
polar-stained  bacteria. 

None  of  the  three  lots  of  pigs  were  thus  free  from  these  bacteria.  It  will  be  noticed 
that  the  mucus  from  four  pigs  was  tested  twice  and  that  the  results  were  not  uniform. 
No  animal  produced  disease  more  than  once  while  one  failed  to  produce  disease  both 
times. 

Pig  No.  303.  January  28,  1890.  This  animal  was  taken  from  a  herd  which  had 
been  purchased  January  25.  The  farm  from  which  it  came  is  said  to  have  had  some 
form  of  swine  disease  on  it  nearly  a  year  ago.  The  thoracic  organs  of  the  pig  were 
normal  in  appearance.  Two  rabbits  were  inoculated,  one  with  mucus  from  the 
larynx,  the  other  with  mucus  from  the  pharynx.  Both  succumbed  on  the  third  and 
fourth  day,  respectively,  to  exudative  peritonitis.  In  the  exudate  the  swine-plague 
bacteria  were  quite  abundant. 

December  24,  1890.  No.  447,  about  4  months  old,  received  yesterday  with  a  lot  of 
other  pigs  from  a  farm  which  has  been  free  from  disease  for  several  years.  The  pig 
was  killed  by  bleeding,  and  although  it  seemed  well,  the  anterior  half  of  both  lungs 
was  found  diseased.  The  diseased  lobes  were  of  a  pale  red  appearance  and  seemed 
cedematous  rather  than  hepatized.  There  was  considerable  muco-puruleut  secretion 
in  the  smaller  bronchi.  In  the  terminal  bronchi  of  the  principal  lobe  some  lung 
worms. 

One  rabbit  was  inoculated  subcutaneously  with  a  particle  of  lung  tissue  and  two 
with  mucus  from  base  of  tongue.  The  former  remained  well ;  both  the  latter  died. 
One  died  within  40  hours  with  considerable  local  purulent  infiltration  of  skin  and 
subcutis.  Spleen  enlarged,  containing  bacteria  showing  polar  stain.  Culture  on  agar 
from  spleen  contains  only  swine-plague  bacteria.  The  second  rabbit  died  in  3  days, 
with  very  extensive  subcutaneous  infiltration  and  exudative  peritonitis.  Spleen  en- 
larged and  dark  colored.  In  the  organs  few  bacteria,  in  the  exudafce  a  large  number. 
Cultures  from  spleen  and  exudate  contain  only  swine-plague  bacteria.  In  order  to 
test  the  virulence  of  these  bacteria  in  pure  cultures,  an  adult  rabbit  was  inoculated 
subcutaneously  with  an  equivalent  of  one  five-hundredths  cubic  centimetre  bouillon 
culture  diluted  in  bouillon.  The  rabbit  died  on  the  fourth  day  with  lesions  like 
those  of  the  preceding  case. 

5.  The  results  thus  far  obtained  must  not  lead  us  to  infer  that  all 
swine  carry  with  them  bacteria  closely  allied  to  swine-plague  bacteria. 
Some  herds  are  entirely  free  from  them,  as  the  following  statements  will 
show : 

Pigs  Nos.  116  to  133  were  received  January  4,  1889,  from  a  place  in  the  District  of 
Columbia  where  swine  diseases  have  not  prevailed  for  a  number  of  years,  and  where 
much  care  is  bestowed  on  the  rearing  of  swine.  From  four  of  these,  nasal  mucus  was 
collected  and  four  rabbits  inoculated  subcutaneously  with  one  or  more  drops.  All 
remained  well. 

From  another  lot  of  eight,  received  February  4,  two  were  tested.  The  results  were 
likewise  negative. 


116 

To  test  the  matter  somewhat  more  thoroughly  in  subsequent  cases, 
the  animals  to  be  examined  were  killed  and  mucus  taken  from  various 
places  in  the  upper  air  passages. 

No.  205,  one  of  a  lot  regarded  healthy,  killed  June  15, 1889.  Pericardium  firmly 
adherent  to  the  heart,  Three  rabbits  inoculated  with  mucus  from  posterior  nares,  the 
base  of  tongue  and  from  below  vocal  cords.  All  remained  well. 

No.  207,  from  another  lot,  killed  on  the  same  day.  The  organs  were  in  general 
healthy  with  the  exception  of  the  large  intestine.  The  mucous  membrane  appeared 
to  be  in  a  state  of  mucous  degeneration.  It  was  swollen,  partly  translucent.  On 
valve  and  along  colon  small  patches  of  a  thin,  friable,  yellowish  deposit.  Five  rab- 
bits were  inoculated — two  from  this  deposit,  three  with  mucus  from  trachea,  poster- 
ior nares,  and  base  of  tongue.  All  remained  well, 

It  would  be  going  too  far  to  maintain  that  all  forms  of  lung  disease 
were  the  result  of  the  invasion  of  swine-plague  bacteria.  The  absence 
of  these  bacteria  is  well  illustrated  by  an  outbreak  of  hog  cholora  in- 
vestigated in  the  fall  of  1887,  and  reported  in  the  special  report  on  hog 
cholera,  pp.  39-52, 

In  about  one-half  of  the  fifty  cases  there  was  some  disease  of  the  lungs. 
This  was  in  part  simple  collapse,  in  part  broncho-pneumonia  involving 
one  of  the  small  ventral  lobes.  Of  the  sixteen  rabbits  inoculated  with 
particles  of  diseased  lung  tissue  from  sixteen  cases,  four  survived  and 
the  remainder  died  of  hog  cholera.  Swine-plague  bacteria  were  not  de- 
tected. It  is  reasonable  to  assume  that  if  they  had  been  present  in  the 
upper  air  passages  they  would  have  sooner  or  later  invaded  the  diseased 
lung  tissue  and  appeared  in  the  inoculated  rabbits. 

In  addition  to  the  foregoing  experiments  a  few  inoculations  into  rab- 
bits were  made  with  mucus  from  the  caecum  of  healthy  pigs,  but  they 
were  negative  so  far  as  swine-plague  bacteria  are  concerned.  The 
mucus  was  taken  from  the  crypts  on  the  ileocsecal  valve  and  the  sur- 
face of  the  patch  in  which  they  are  imbedded. 

Caecum  No.  1,  One  rabbit  and  two  mice  inoculated  subcutaneously.    No  result. 

Caecum  No.  2.  One  rabbit  inoculated.  Died  in  8  days.  Extensive  sauguinolent  and 
purulent  inflammation  of  the  subcutis  of  abdomen.  Peyer's  patches  swollen  and  pig- 
mented.  The  appendix  of  caecum  swollen,  blackish;  ulceia  on  mucous  surface.  Cul- 
tures from  internal  organs  wholly  negative. 

Caecum  No.  3.  One  rabbit  inoculated.  Died  in  8  days.  Subcutis  and  appendix  as  in 
preceding  case.  Cultures  sterile. 

Caecum  No.  4.  One  rabbit  inoculated.  Died  in  11  days.  On  thigh,  an  abscess  be- 
tween muscles  half  as  large  as  a  hen's  egg.  Center  disintegrated  into  a  curdy  mass. 
No  other  lesions.  In  the  pus  of  abscess  large  numbers  of  bacilli  of  various  lengths, 
staining  feebly.  They  fail  to  grow  in  culture  media.  Internal  organs  free  from 
bacteria. 

It  may  be  claimed  that  the  presence  of  swine-plague  bacteria  on  the 
mucous  membranes  of  healthy  swine  and  other  domesticated  animals 
is  an  argument  against  the  specific  character  of  swine-plague  bacteria, 
and  hence  against  the  existence  of  a  specific  disease  induced  by  them. 
We  have  already  met  this  argument  by  the  numerous  successful  inocu- 
lations of  swine-plague  bacteria  into  healthy  swine,  by  which  a  disease 


117 

like  the  natural  disease  has  been  produced.  The  attenuated  virulence 
of  the  bacteria  in  the  air  passages  makes  it  probable  that  few  of  them 
are  able  to  produce  disease  excepting  in  a  secondary  role. 

There  are  two  infectious  diseases  in  man  which  in  this  respect  offer 
some  striking  analogies  to  swine  plague.  The  disease  known  as  croup- 
ous  pneumonia  is  chiefly  associated  with  bacteria  (Diplococcus  pneu- 
monias) bearing  much  resemblance  to  swine-plague  bacteria.  These 
bacteria  are  now  regarded  as  the  chief,  if  not  the  only,  cause  of  pneu- 
monia. Strangely  enough,  bacteria  not  distinguishable  from  these  are 
occasionally  encountered  in  the  saliva  of  healthy  persons.  Senator, 
Pasteur,  and  Sternberg  wore  among  the  first  to  call  attention  to  the 
fact  that  rabbits  inoculated  with  sputum  may  die  of  septictsmia,  and 
the  bacteria  found  in  the  internal  organs  of  these  rabbits  were  identi- 
fied subsequently  with  the  bacteria  of  pneumonia.  We  have  thus  a 
complete  analogy  between  swine-plague  and  croupous  pneumonia. 

In  another  disease  facts  of  similar  nature  have  recently  come  to 
light.  Eoux  and  Yersin*  have  found  in  the  mouths  of  about  10  per- 
cent, of  all  healthy  persons  examined  bacilli  which  have  no  pathogenic 
effect,  but  which  resemble  closely  the  bacilli  of  diphtheria,  which,  in 
fact,  they  regard  as  very  attenuated  forms  of  the  diphtheria  bacillus. 
Loftier  and  others  had  previously  found  similar  bacilli  in  the  mouths 
of  healthy  persons. 

There  are  several  important  questions  raised  by  the  discovery  of  at- 
tenuated forms  of  disease-germs  in  the  surroundings,  and  in  the  body 
of  animals.  Do  these  bacteria  belong  to  the  same  species  as  the  viru- 
lent forms,  and,  if  so,  can  they  gain  virulence  enough  under  certain 
circumstances  to  produce  disease?  That  pathogenic  bacteria  may  gain 
in  virulence  has  been  shown  by  Pasteur,  Roux,  and  others.  Whether 
this  applies  to  all  kinds  of  disease-germs  may  be  reasonably  doubted, 
and  the  experiments  thus  far  tried  by  us  to  increase  the  virulence  of 
attenuated  hog  cholera  and  swine-plague  bacteria  have  shown  that  by 
passing  them  through  susceptible  animals  no  decided  increase  in  viru- 
lence is  observed.  On  the  other  hand,  so  far  as  methods  are  able  to 
inform  us,  these  same  attenuated  bacteria  found  in  the  air  passages  of 
healthy  animals,  and  the  swine-plague  bacteria  proper  found  in  disease, 
do  belong  to  the  same  species,  and  must  be  regarded  as  simple  varieties. 

These  discoveries  also  point  out  that  the  one  property  of  pathogenic 
bacteria  which  must  receive  special  attention  is  their  relative  virulence. 
This  seems  to  be  the  one  factor  which  determines  the  severity  and  the 
commuuicability  of  infectious  diseases. 

*  Anuales  de  1'  Institut  Pasteur,  1890,  p.  409. 


BRIEF  REVIEW  OF  THE  INVESTIGATIONS  OF  OTHER  OBSERVERS. 

AMERICAN. 

Of  the  work  done  in  investigating  the  diseases  of  swine  that  of  Dr.  F. 
S.  Billings  seems  to  have  aroused  much  attention,  chiefly  because  of  the 
polemical  attitude  which  he  has  assumed  and  the  peculiar  manner  in 
which  he  has  criticised  the  work  of  the  Bureau  of  Animal  Industry. 
His  results  are  contained  in  a  volume  of  414  pages,  published  by  the 
University  of  Nebraska  in  1888,  in  connection  with  which  institution 
the  work  was  carried  on. 

In  this  volume  Billings  has  given  us  very  little  opportunity  to  dis- 
cover how  much  work  was  actually  done  in  arriving  at  the  various  theo- 
ries and  conclusions  contained  in  the  volume.  The  statements  of  ex- 
periments are  exceedingly  meager  and  the  bacteriological  work  very 
unsatisfactory. 

It  is  evident  that  in  work  of  this  kind  the  discovery  of  the  causes  of 
disease  is  the  fundamental  problem,  and  all  other  problems  must  at  the 
outset  be  subservient  to  this  one.  The  bacteriological  work  is  there- 
fore the  most  important.  A  perusal  of  the  report  of  Billings  shows  that 
he  has  contributed  nothing  whatever  to  the  elucidation  of  this  problem, 
while  his  obstructive  attitude  has  confused  and  retarded  the  progress 
in  the  right  direction  in  a  marked  degree,  as  the  following  statements 
conclusively  prove : 

He  has  assumed  the  position  that  there  is  but  one  infectious  swine 
disease  in  the  country,  while  the  investigations  of  the  Bureau  of  Am- 
inal  Industry  have  maintained  that  there  are  at  least  two.  The  various 
criticisms  which  Billings  has  written  of  the  work  of  the  Bureau  need  not 
engage  our  attention  here.  They  are  interesting  enough  to  be  read  in 
the  original,  but  they  all  collapse  in  view  of  investigations  published 
in  the  present  volume.  That  the  earlier  investigations  of  the  Bureau 
on  swine  plague  were  not  absolutely  demonstrative  no  one  will  deny. 
That  they,  however,  pointed  very  directly  to  another  disease  is  shown 
by  pathological  as  well  as  bacteriological  considerations — a  severe 
pleuro-pneumonia  associated  with  specific  pathogenic  bacteria  easily 
differentiated  from  the  bacteria  causing  hog  cholera.  The  repeated 
occurrence  of  pathogenic  bacteria  in  case  after  case  of  an  outbreak  could 
not  well  be  overlooked  or  explained  away  by  any  pathological  consider- 
ations. The  duty  of  an  investigator  in  another  section  of  the  country 

118 


119 

would  have  been  the  careful  investigation  of  his  own  territory  as  to  the 
presence  or  absence  of  such  diseases. 

What  is  the  nature  of  the  bacteria  described  by  Billings  as  the  cause 
of  the  infectious  swine  diseases  ? 

If  we  examine  pages  103-116  of  his  report  we  shall  find  a  brief  ac- 
count of  the  bacteria  in  question.  If  we  examine  his  description  and 
figures  on  page  104,  and  compare  them  with  the  swine-plague  bacteria 
described  in  the  foregoing  pages,  it  will  be  observed  that  he  has  before 
him  swine-plague  bacteria  and  not  hog-cholera  bacilli.  Of  this  he  seems 
to  be  himself  aware,  for  on  page  111  he  states  that  the  hog-cholera 
bacteria,  as  described  in  the  reports  of  the  Bureau,  have  no  existence, 
t.  e.,  are  fictitious. 

Next,  the  growth  on  potato  as  observed  by  Billings  is  anything  but 
that  of  swine-plague  bacteria.  It  may  be  that  of  hog-cholera  bacilli  or 
of  allied  intestinal  bacteria. 

The  remarks  about  gelatine  cultures  may  apply  to  at  least  a  dozen 
species  of  bacteria. 

The  observations  about  the  movement  of  these  bacteria  is  equally  in- 
definite. It  might  apply  very  well  to  the  Brownian  motion  of  swine- 
plague  bacteria,  but  it  certainly  does  not  describe  the  rapid  motion 
across  the  microscopic  field  so  characteristic  of  hog'cholera  bacilli.* 

This  very  incomplete  description  of  the  bacteria  found  by  Billings 
leaves  us,  therefore,  entirely  in  the  dark.  The  form,  mode  of  staining, 
and  the  motility,  apply  to  swine-plague  bacteria,  the  potato  growth, 
perhaps,  to  hog-cholera  bacilli.  How  can  we  reconcile  this  conflicting 
account  ?  Bearing  in  mind  the  fact  that  in  the  organs  of  swine  which 
have  succumbed  after  extensive  lesions  of  the  lungs  and  large  intes- 
tine, it  is  not  an  uncommon  thing  to  find  various,  forms  of  bacteria, 
bacillus  coli,  non-motile  bacilli  (also  found  in  intestines),  streptococci, 
gas-producing,  spore-bearing  bacilli,  etc.,  either  alone  or  associated 
with  the  real  cause  of  the  disease,  we  find  ourselves  unable  to  explain 
his  discovery  because  we  have  no  full  and  accurate  report  of  investiga- 
tions actually  carried  out.  The  description  he  gives  may  apply  so  far 
as  we  know  to  the  bacteria  found  in  one  hog,  in  five  hogs,  or  in  a  hun- 
dred hogs.  It  is  obvious  that  the  amount  of  conviction  his  statements 
carry  depends  entirely  upon  the  number  of  animals  to  which  such  state- 
ments apply. 

An  explanation  which  covers  the  ground  of  the  statements  made  by 
Billings  fairly  well  is  one  which  takes  into  account  the  mingling  of  two 
diseases.  Since  1886  we  have  seen  very  few  outbreaks  of  hog  cholera 
not  associated  with  swine  plague.  The  investigations  recorded  in  these 
pages  show  how  frequently  it  may  occur  that  a  culture  may  contain 

*  In  his  report  on  the  "corn-stalk"  disease  of  cattle,  page  18G,  Billings  seems  to 
have  lost  his  doubts  concerning  the  motility  of  the  hog-cholera  (swine-plague  of 
Billings)  bacillus.  He  there  considers  it  by  comparison  "to  possess  most  active 
movements." 


120 

both  swine-plague  and  hog  cholera  bacilli,  or  that  the  cultures  from  one 
animal  contain  only  swine-plague  bacteria,  those  from  another  of  the 
same  herd  only  hog-cholera  bacilli.  Again  this  report  illustrates  that 
we  may  be  called  upon  to  investigate  an  outbreak  of  swine  disease  in 
which  hog  cholera  bacilli  are  demonstrable  in  every  case,  and  in  the 
succeeding  one  we  may  find  only  swine  plague  bacteria  or  a  mixture  of 
both  germs. 

It  is  highly  probable  that  Billings  had  under  observation  now  one 
germ,  now  another,  and  occasionally  a  mixture  of  both.  With  this  ex- 
planation *  in  mind  we  may  easily  interpret  the  conflicting  account  of 
the  bacteria  given  by  Billings,  especially  if  such  statements  are  based 
on  a  small  number  of  cases  only.  This  explanation  is  the  more  plaus- 
ible when  we  turn  to  the  method  used  by  Billings  in  obtaining  pure 
cultures  from  animals.  While,  on  the  one  hand,  his  cultivation  methods 
were  insufficient  to  determine  accurately  whether  cultures  contain  more 
than  one  organism  or  not,  he  unwittingly  assumes,  on  the  other  hand, 
first,  that  the  bodies  of  diseased  swine  always  contain  only  one  kind  of 
bacteria,  and,  second,  that  this  kind  is  always  the  same.  These  as- 
sumptions anyone  will  recognize  on  reading  page  103  of  his  report. 
How  much  information  can  be  obtained  by  such  deductive  method  of 
pursuing  a  most  inductive  branch  of  scientific  investigation,  the  reader 
must  be  allowed  to  judge  for  himself.  It  may  be  noted,  however,  that 
such  vicious  methods  furnish  ample  material  for  the  attack  upon  work 
done  by  others. 

Again,  the  examination  of  5  hogs,  or  of  500  hogs,  made  over  a  lim- 
ited territory  with  a  uniform  result,  does  not  permit  us  to  generalize 
negatively  on  the  swine  diseases  of  the  remaining  millions  scattered 
over  the  whole  country.  This  attitude  is  to  be  regretted  the  more 

*  A  good  illustration  of  the  plausibility  of  this  theory  may  be  found  on  pp.  191-197 
of  the  report  of  Billings,  where  the  results  of  some  inoculations  of  smaller  animals 
are  detailed,  These  may  be  tabulated. 

One  rabbit,  inoculated  with  one-half  cubic  centimetre  bouillon  culture,  subcu- 
taneously,  May  14,  dies  in  3  days. 

One  squirrel,  inoculated  with  one-half  cubic  centimetre  bouillon  culture,  subcu- 
taneously,  May  14,  dies  in  3  days. 

One  rabbit,  inoculated  with  one-fourth  cubic  centimetre  spleen  emulsion  of  preced. 
ing  rabbit,  May  17,  dies  in  6  days. 

One  rabbit,  inoculated  with  seven  drops  of  blood,  etc.,  from  pig,  subcutaueously, 
May  23,  dies  in  1-J  days. 

In  this  series  the  dose  injected  into  the  first  rabbit  ia  too  large  to  bring  out  the 
differential  characters  of  either  hog-cholera  or  swine-plague  germs.  In  the  second 
rabbit  death  was  probably  due  to  hog-cholera  bacilli.  In  the  third  it  was  certainly 
due  to  swine  plague,  since  the  most  virulent  hog-cholera  bacilli  would  not  destroy 
rabbits  in  the  dose  used,  in  less  than  4  to  7  days.  In  the  report  on  the  corn-stalk  dis- 
ease already  referred  to  (1889),  Billings  states  that  a  certain  germ  could  not  "be 
that  of  swine  plague  (hog  cholera)  on  account  of  its  acute  fatality."  These  later 
opinions  are  refreshing  in  being  in  the  right  direction  as  far  as  hog  cholera  is  con- 
cerned. 


121 

when  we  reflect  on  the  fact  that  the  area  of  diseases  is  largely  defined 
by  geographical,  climatic,  and  economic  factors. 

In  his  report,  Billings  throughout  denies  the  existence  of  the  hog- 
cholera  bacillus  first  described  in  the  Bureau  Report  for  1885.  This 
denial  may  be  found  scattered  throughout  the  report.  Then  we  must 
assume  that  he  considered  the  swine-plague  bacteria  as  the  cause  of 
American  swine  diseases.  This  assumption  is  proven  by  his  repeated, 
almost  continuous,  discussion  of  the  European  Schweineseuche  and.  Wild- 
seuche.*  This  continual  dragging  in  of  the  work  of  European  observers 
can  only  be  understood  by  assuming  a  great  similarity  or  a  possible 
identity  between  the  bacteria  in  the  hands  of  Billings  and  those  of 
Sclm-eineseuche,  as  described  by  Loftier,  Schiitz,  Hiippe,  and  others.  On 
the  other  hand,  the  pathological  appearances  in  these  diseases  differed 
so  greatly  that  Billings  found  it  necessary  to  occupy  the  greater  part 
of  his  report  in  needlessly  pointing  out  likenesses  and  differences. 

Up  to  this  point,  then,  it  seems  that  Billings  regarded  his  swine  dis- 
ease bacteria  as  the  same  morphologically  with  the  German  Wildseuche, 
and  that  he  denied  the  existence  of  the  hog  cholera  bacillus.  Mean- 
while we  studied  his  publications  and  made  every  effort  to  determine 
what  bacteria  he  was  studying,  but  without  success,  owing  to  the  im- 
perfect diagnosis  given  and  the  peculiar  intermingling  of  the  proper- 
ties of  the  bacteria  of  hog  cholera  and  swine  plague  found  in  his  report. 

In  1889,  however,  to  our  surprise,  the  commission  appointed  to  throw 
some  light  on  this  matter  found  Billings  in  possession  of  real  hog-chol- 
era bacilli.  Cultures  were  sent  by  him  to  Berlin,  where  a  comparison 
of  these  cultures  with  some  sent  from  this  laboratory  likewise  demon- 
strated that  his  swine-plague  bacteria  were  identical  with  the  hog- 
cholera  bacilli  discovered  in  the  Bureau  laboratory  in  1885,t  nearly  a 
year  before  Billings  began  his  work  in  Nebraska. 

All  these  facts  make  it  highly  probable  that  Billings  had  unwittingly 
studied  at  least  several  kinds  of  bacteria,  among  which  the  swine-plague 
bacteria  of  this  report  must  have  played  an  important  part.  In  a  recent 
article}  on  swine  diseases,  prepared  under  Hiippe,  the  author  mentions 
the  fact  that  Billings  had  sent  cultures  at  two  different  times,  which, 
though  considered  by  the  sender  as  identical,  were  really  quite  differ- 
ent. In  another  article  Caueva,§  working  under  Hiippe  in  Fresenius' 
laboratory,  endeavors  to  group  the  various  bacteria  producing  swine 
disease,  and  in  so  doing  separates  the  bacteria  sent  by  Billings  from 
hog-cholera  bacilli,  because  the  former  were  less  actively  motile,  coagu- 
lated milk,  and  produced  only  local  reaction  after  subcutaneous  inocu- 
lation. They  also  failed  to  infect  by  feeding.  While  these  bacteria 
may  represent  an  attenuated  variety  of  hog-cholera  bacilli  so  far  as  their 

*  Compare  also  page  141  of  this  report. 
t  Frosch.  Zeitscbrift  fur  Hygiene,  ix,  S.  235. 
tBuuzl-Federn.  Archiv  f.  Hygieue,  xn,  S.  198. 
$  Ceutralblatt  f.  Bakteriologie.  ix,  8.  557. 


122 

virulence  is  concerned,  none  of  the  hog-cholera  bacilli  from  numer- 
ous and  widely  separated  localities  examined  in  this  laboratory  ever 
produced  coagulation  of  milk.  Bacteria  of  the  latter  class  are  chiefly 
harmless  intestinal  parasites  which  closely  resemble  hog-cholera  bacilli 
(bacillus  coli)  and  which  occasionally  appear  in  cultures  from  cases  of 
swine  disease. 

If,  therefore,  Billings  had  found  the  hog-cholera  bacillus  the  question 
arises :  Why  did  he  fill  up  his  report  with  pages  of  extracts,  comment, 
and  criticism  of  the  European  Schweineseuche,  when  the  bacteria  of  hog 
cholera  and  ScliiceincseucTie  are  wholly  different,  as  every  observer  has 
admitted  who  has  compared  them  ?  Such  discussions  are  not  only  use- 
less, but  misleading,  when  brought  to  bear  upon  the  condition  of  things 
in  our  own  country.  In  view  of  these  facts  the  question  also  arises : 
Why  did  Billings  so  vehemently  oppose  the  hog-cholera  bacillus 
described  in  the  Bureau  Report  of  1885,  and  found  by  us  to  exist  in 
Nebraska  before  Billings  entered  upon  his  work  there,  if  he  had  it 
under  observation  himself?  These  contradictory  positions  can  only  be 
interpreted  by  the  assumption  made  above,  that  Billings  had  at  first 
one  or  several  kinds  of  bacteria  under  observation  differing  from  the 
true  hog-cholera  bacillus. 

If  we  are  nevertheless  to  conclude  that  Billings  has  finally  settled 
upon  hog-cholera  bacilli  as  the  cause  of  swine  disease  in  Nebraska,  any 
further  comment  on  his  work  could  only  be  taken  up  under  hog  cholera. 
The  question  whether  there  is  another  disease  besides  hog  cholera  is 
settled  in  the  affirmative  by  the  work  reported  in  these  pages.  This 
second  disease  seems  to  be  in  fact  the  disease  which  Billings  has  had 
in  mind  in  his  controversies,  and  his  criticisms  of  American  and  for- 
eign work.  Unfortunately,  however,  it  has  turned  out  that  he  has 
mistaken  the  disease,  and  now  his  opposition  strangely  enough  has 
shifted  towards  the  swine-plague  bacteria,  since  an  attitude  of  opposi- 
tion towards  hog  cholera  could  no  longer  be  maintained.* 

It  is  clear  to  any  unbiased  reader  that  work  which  fails  to  grasp  any 
positive  truth,  and  is  continually  shifting  its  base  to  avoid  the  necessary 
consequences  of  serious  errors,  and  which  goes  beyond  its  confines  not 
only  to  criticise,  but  to  discredit  in  every  manner  possible  the  work  of 
other  observers,  can  not  be  seriously  taken  into  consideration  as  advanc- 
ing in  the  least  degree  our  positive  knowledge. 

During  the  years  1887-'89,  Professor  Welch,  in  conjunction  with  A. 
W.  Clement,  V.  S.,  and  F.  L.  Russell,  V.  S.,  investigated  a  number  of 
outbreaks  of  swine  disease  in  the  neighborhood  of  Baltimore,  Md.  In 

*  A  simple  statement  of  the  position  of  Billings  would  read  thus : 

1.  Opposition  to  hog-cholera  bacteria  discovered  in  Bureau  laboratory  in  1885. 
Evidence  in  his  writings  all  points  to  swine  plague. 

2.  Discovery  by  commission  and  German  observers  that  his  gejm  and  the  hog- 
cholera  bacillus  are  identical;  hence, 

3.  Opposition  to  swiue-plague  bacteria. 


123 

a  preliminary  report  published  in  the  Johns  Hopkins  Hospital  Bulletin, 
December,  1889,  Welch  gives  a  brief  summary  of  the  results  obtained 
np  to  that  date.  These  investigators  encountered  in  some  herds  only 
hog-cholera  bacilli,  in  others  only  swine-plague  bacteria,  and  in  still 
others  both  kinds  of  bacteria.  They  have  not  been  able  to  fix  upon 
any  anatomical  differences  between  the  herds  in  which  hog-cholera  ba- 
cilli were  found  and  those  in  which  only  swine-plague  bacteria  were  de- 
tected, for  in  all  cases  intestinal  lesions  were  present.  The  description 
of  the  two  kinds  of  bacteria  agrees  in  every  respect  with  that  published 
in  the  various  reports  of  the  Bureau  of  Animal  Industry  since  1885. 
With  both  the  authors  were  able  to  produce  disease  in  swine,  intestinal 
lesions  with  hog-cholera  bacilli  and  lung  lesions,  associated  with  inflam- 
mation of  the  serous  membranes,  with  swine-plague  bacteria. 

While  the  results  agree  in  every  particular  with  those  obtained  by  us, 
Welch  expresses  himself  with  caution  concerning  the  role  of  swine- 
plague  bacteria,  because  in  the  herds  studied  none  were  free  from  intes- 
tinal lesions.  He  suggests  the  possibility  of  overlooking  hog-cholera 
bacilli  because  they  may  remain  limited  to  the  intestinal  tract,  a  possi- 
bility to  which  we  have  called  attention  in  the  report  for  1887-'88,  and 
in  these  pages.  On  the  other  hand  the  facts  that  pneumonia  may  be 
produced  by  swine-plague  bacteria,  and  that  a  swine  disease  exists  in 
Germany  in  which  pneumonia  without  intestinal  lesions  is  associated 
with  swine  plague  bacteria,  "  suggest  that  this  organism  is  also  the 
cause  of  a  similar  affection  in  this  country." 

In  1889  and  1890  Dr.  J.  A.  Jeffries*  made  bacteriological  observa- 
tions in  several  outbreaks  of  swine  disease  of  an  infectious  character. 
In  one  pig  were  found  a  large  spore-bearing  bacillus,  a  short  bacillus,, 
and  swine-plague  bacteria.t  The  short  bacilli  Jeffries  found  non-path- 
ogenic, while  the  third  form,  the  swine-plague  bacteria,  he  considers 
the  cause  of  the  disease. 

T,he  description  of  the  pathological  appearances  of  the  diseased  pigs 
and  of  the  swine-plague  bacteria  found  by  him,  taken  together  with  the 
inoculation  experiments  and  the  absence  of  hog-cholera  bacilli,  make 
it  pretty  certain  that  the  disease  was  identical  with  that  described  in 
these  pages. 

Through  the  kindness  of  Dr.  Jeffries  a  culture  of  the  swine.plague 
bacteria  was  sent  to  the  laboratory,  where  a  comparative  study  of  the 
morphological  and  pathogenic  characters  showed  them  to  be  an  at- 
tenuated variety  of  swine-plague  bacteria,  not  distinguishable  from 
those  described  in  these  pages.  A  few  of  the  inoculations  on  rabbits 

'Etiology  of  two  outbreaks  of  disease  among  hogs.  The  Journal  of  Cornp.  Medi- 
cine, December,  1890. 

tThe  spore-bearing  bacillus  I  have  found  in  many  outbreaks  as  the  result  of  post- 
mortem growth.  In  some  pigs  sections  from  every  organ  show  these  long  wavy  fila- 
ments filling  np  the  capillaries  and  penetrating  the  tissue  in  all  directions.  See  also 
page  80  of  this  report. 


124 

are  given  to  illustrate  the  variety  of  lesions  which  these  bacteria  may 
produce. 

The  culture  was  first  tested  by  plate  cultures  and  two  rabbits  inoculated  from  a 
bouillon  sub-culture. 

June  3,  1890.  One  rabbit  received  one-eighth  cubic  centimetre  subcutaneously,  and 
one  one-eighth  cubic  centimetre  into  an  ear  vein. 

In  both  the  temperature  was  between  105°  and  106°  F.  on  the  sixth  day.  On  the 
tenth  day  the  first  had  recovered;  the  second,  unable  to  move  hind  limbs,  was  chloro- 
formed. The  only  lesions  observed  were  two  abscesses,  one  on  the  right  tarsus,  the 
other  on  left  elbow  joint,  both  communicating  with  the  joint  cavity. 

The  culture  was  thus  considerably  attenuated.  Nothing  more  was  done  till  Decem- 
ber, when  the  same  culture,  passed  through  a  series  of  agar  tubes  meanwhile,  was 
used,  because  attenuated,  for  some  preliminary  immunity  experiments  on  rabbits. 
The  virulence  of  the  bacteria  was  much  greater  now,  as  the  following  inoculations 
prove.  Attention  is  called  to  the  great  variation  in  the  lesions  produced,  and  to  the 
pneumonia  in  No.  5. 

December  8,  1890.  Two  rabbits  (Nos.  1,  2)  received  subcutaneously  one-eighth  cubic 
centimetre  bouillon  culture,  and  two  (Nos.  3,  4)  the  same  dose  into  an  ear  vein. 

No.  1  dies  in  7  days  with  extensive  purulent  infiltration  of  the  snbcutis  over  abdo- 
men and  thorax,  purulent  peritonitis  and  pleuritis. 

No.  2  survives. 

No.  3  very  sick  on  the  fifth  day  and  chloroformed.  A  subcutaneous  purulent  in- 
filtration extends  from  place  of  injection  on  the  ear  over  the  greater  part  of  face. 
No  other  lesions  observed. 

No.  4.  Temperature  on  third  day  105.5°  F.  Dies  on  the  fifth  day  with  peritonitis 
and  pleuvitis.  The  exudate  stretches  in  the  form  of  delicate  grayish  viscid  threads 
between  coils  of  intestine  when  these  are  lifted  up,  and  from  chest-wall  to  pleura  of 
lungs.  The  exudate  a  mixture  of  leucocytes  and  immense  numbers  of  bacteria. 

As  these  experiments  were  designed  to  find  a  dose  which  would  not  prove  fatal 
they  were  repeated. 

December  16.  Two  rabbits  (Nos.  5,  6)  receive  a  subcutaneous  injection  of  one-eight- 
hundredth  cubic  centimetre  bouillon  culture,  and  two  (Nos.  7,  8)  an  intravenous  in- 
jection of  the  same  dose. 

In  all  cases  the  culture  was  diluted  and  one-fourth  cubic  centimetre  of  the  dilution 
injected. 

No.  5  dies  in  9  days.  Extensive  purulent  infiltration  of  subcutis  over  abdomen  and 
part  of  thorax.  Exudative  peritonitis  absent.  Purulent  pleuritis  with  exudate  es- 
pecially abundant  on  right  lung  and  chest-wall.  Hepatization  of  the  two  small  anterior 
and  portion  of  principal  lobe  of  same  side.  The  hepatized  lobes  in  part  dark  red  and 
pale  red,  firm  and  enlarged.  Epicardiuin  covered  with  a  membranous  exudate.  In 
the  exudate  numerous  bacteria  showing  the  polar  stain. 

No.  6.  Temperature  on  second  day  105°  F.  Dies  on  sixth  day.  Extensive  purulent 
and  sauguiuolent  infiltration  of  the  subcutis  as  in  preceding  case.  Spleen  barely  en- 
larged, somewhat  darker  than  normal.  No  peritonitis  or  pleuritis. 

No.  7.  Temperature  105.2°  F.  on  second  day.  Dies  on  thirteenth  day.  Extensive 
subcutaneous  infiltration  as  in  preceding  case.  Straw-colored,  elastic  membranous 
exudate  on  liver,  spleen,  and  caecum,  and  between  coils  of  large  intestine,  matting 
the  various  organs  together.  The  exudate  is  easily  pulled  away  and  consists  of  fatty 
pus  cells  and  immense  numbers  of  swine-plague  bacteria.  In  pleural  sacs  some 
serous  exudate.  Pale  red  hepatizatiou  of  a  small  portion  of  the  small  anterior  lobes 
of  right  lung.  Spleen  moderately  enlarged,  dark.  Peyer's  patches  pigmented. 

In  November,  1890,  Prof.  T.  J.  Burrill,  of  Illinois  University,  sent 
two  agar  cultures  of  bacteria  obtained  from  an  outbreak  of  swine  dis- 


125 

ease  in  Illinois.  Botli  cultures  were  carefully  examined  and  found  to 
contain  only  swine-plague  bacteria.  To  test  the  pathogenic  character 
two  rabbits  were  inoculated.  These  inoculations  prove  the  essential 
identity  of  these  bacteria  with  swine-plague  bacteria. 

November  7.  From  a  bouillon  culture,  1  day  old,  one-tenth  cubic  centimetre  was 
injected  under  the  skin  of  a  large  rabbit. 

November  11.  Rabbit  found  dead  this  morning.  At  point  of  inoculation  purulent 
thickening  of  the  subcutis.  Coacum,  colon  and  rectum  sprinkled  with  hemorrhages. 
Slight  viscid  exudate  on  caecum  which  contains  large  numbers  of  the  injected  bac- 
teria. Liver  and  kidneys  pale.  Spleen  barely  eularged,  dark  in  color.  The  agar 
and  bouillon  cultures  from  blood,  spleen,  and  abdominal  exudate  contain  only  the  in- 
oculated bacteria. 

November  13.  A  rabbit  received  subcutaneously  on  side  of  abdomen  one-tenth 
cubic  centimetre  bouillon  culture  prepared  from  the  second  original  culture.  Rab- 
bit dies  in  40  hours.  A  very  slight  infiltration  at  the  place  of  inoculation.  Spleen 
slightly  enlarged  and  engorged.  In  it  a  considerable  number  of  swine-plague  bact- 
eria showing  the  polar  stain.  Au  agar  culture  from  the  spleen  contains  these 
bacteria  only. 

GERMAN. 

Of  great  interest  and  importance  to  us  are  the  German  investiga- 
tions of  swine  plague  (Scliweineseuclie),  because  this  disease  does  not  ap- 
pear to  be  complicated  with  any  other  disease,  as  is  the  case  in  our  own 
country  where  swine  plague  and  hog  cholera  are  so  frequently  asso- 
ciated with  each  other. 

Probably  the  first  investigation  in  which  swine-plague  bacteria  were 
observed  is  that  of  Loffler.*  Only  one  pig  was  encountered  in  the 
course  of  a  series  of  investigations  on  the  continental  disease  of  swine, 
known  as  rouget  and  Rothlauf,  in  which  these  bacteria  were  found.  In 
this  case  the  lesions  are  given  as  follows  : 

The  skin  of  abdomen,  sexual  organs,  and  neck  of  a  livid  red  ;  enormous  oedema  of 
the  (sub)  cutis  of  the  neck,  extending  backwards  between  forelimbs.  Pharynx  red- 
dened and  swollen.  Laryngeal  and  tracheal  mucosa  intensely  dark  red.  Lungs  but 
slightly  affected ;  on  the  right  some  dark  red  regions,  containing  but  little  air. 
Nothing  abnormal  about  the  heart.  Cloudy  swelling  of  liver  and  kidneys.  Mucosa 
of  stomach  and  upper  portion  of  duodenum  intensely  reddened.  Remainder  of  intes- 
tines unchanged.  Mesenteric  glands  not  enlarged.  Spleen  rather  large,  dark  bluish 
red,  quite  firm. 

The  bacteria  obtained  from  this  case  resembled  those  of  rabbit  septi- 
ca3mia.t  They  killed  inoculated  rabbits  and  mice  in  24  hours.  Guinea- 

*  Arbeiten  a.  d.  kaiserlichen  Gesundheitsamte,  I  (1885),  S.  51. 

t  The  term  rabbit  septicaemia  originated  in  a  series  of  experiments  on  rabbits  by 
Gaftky,  in  1881  (Mittheilungen  a.  d.  Jcaiserl.  Gesundheitsamte  I,  1881,  S.  102),  who  pro- 
duced in  these  animals  by  the  injection  of  polluted  water  a  rapidly  fatal  disease 
caused  by  bacteria  closely  resembling  those  of  swine  plague  and  some  other  animal 
diseases.  (See  p.  141  of  this  report. )  The  writer  found  bacteria  causing  septic  dis- 
eases in  rabbits,  probably  identical  with  these  in  1880  (Journ.  Comp.  Med.  and  Sur- 
gery, Jan.,  1887).  Prior  to  GafFky's  work,  R.  Koch  and  Davaino  had  been  experi- 
menting with  a  similar  disease  in  rabbits. 


126 

pigs  lived  from  2  to  3  days  after  inoculation.  In  all  there  was  extensive 
sero-sanguinolent  infiltration  of  the  subcutis,  starting  from  the  place  of 
inoculation  and  extending  in  some  over  thorax  and  abdomen.  In  one 
the  intestines  were  covered  with  a  sanguinolent  and  fibrinous  exudate. 
Of  three  pigs  inoculated  (probably  with  minimum  doses)  one  died  in 
2  days  with  the  following  lesions : 

Skin  of  abdomen  bluish  red ;  enormous  oedema  of  skin ;  lungs  hypostatic  ;  mucosa 
of  stomach  deeply  reddened ;  spleen  unchanged;  kidneys  parcnchymatous ;  mesen- 
teric  glands  not  swollen. 

This  first  reported  case  is  interesting  in  that  the  lungs  were  not  the 
seat  of  disease. 

The  disease  of  Schiceineseuche  was  established  in  a  more  definite  man- 
ner by  Schiitz  in  investigations  carried  on  in  1885.* 

Since  then  it  has  been  generally  recognized  as  a  disease  distinct  from 
Eotlilauf.  The  material  with  which  Schiitz  worked  at  this  time  con- 
sisted of — 

1.  The  stomachs,  spleens,  and  livers  of  three  pigs,  more  or  less  decom- 
posed, June  15, 1885. 

2.  The  stomachs  and  spleens  of  several  pigs,  August  27,  from  Putlitz. 

3.  The  trunks  of  two  pigs,  November  19,  from  Putlitz. 

4.  Two  entire  pigs,  December  13,  from  Putlitz. 

In  a  footnote  the  author  states  that  several  additional  cases  of  this 
disease  had  come  under  his  observation  subsequently. 

In  the  four  pigs  of  which  Schiitz  was  enabled  to  examine  the  viscera, 
all  were  affected  with  more  or  less  hepatization  of  the  lungs  associated 
with  pleuritis,  more  rarely  with  pericarditis.  In  one  of  these  four  cases 
there  was  found,  in  addition  to  lung  disease,  peculiar  caseous  degen- 
eration of  the  joints  of  the  limbs,  involving  the  bones  and  surrounding 
muscles.  The  various  lymphatic  glands  were  greatly  enlarged  and  con- 
tained cavities  filled  with  grayish  yellow,  semi-liquid  masses.t  In  the  dis- 
eased lungs  were  disseminated  yellowish  necrotic  foci  varying  in  size. 

From  all  the  cases  examined  bacteria  were  obtained  which  were  evi- 
dently the  same.  Schiitz  described  them  as  follows : 

When  stained  with  gentian  violet  they  show  in  their  central  portions  an  unstained 
region  surrounded  by  a  layer  stained  blue.  The  thickness  of  this  layer  is  greater  at 
the  poles,  so  that  the  extremities  appear  more  deeply  stained  than  the  sides.  When 
deeply  stained  they  appear  uniformly  blue.  As  these  organisms  stand  between  mi- 
crococci  and  bacilli,  they  may  be  called  bacteria.  They  are  1.2  fi  long  and  0.4  /j.  to  0.5 
H  broad.  They  multiply  in  the  following  manner:  They  become  twice  as  long  as 
broad ;  show  distinctly  rounded  extremities,  and  stain  like  the  organisms  of  rabbit 
septicaemia  and  fowl  cholera,  so  that  between  the  deeply  stained  ends  about  one-half 
or  a  third  of  the  entire  length  remains  unstained.  Careful  examination  shows,  how- 
ever, that  the  colored  end  pieces  are  connected  with  each  other  by  a  fine  line  which 
passes  from  one  to  another  on  each  side.  The  end  pieces  then  separate  and  the  me- 
dian portion  disappears.  The  former  are  at  first  spherical,  but  very  soon  assume  an 
oval  form.  Hence  from  every  organism  two  new  individuals  arise  by  division,  in 

*  Loo.  cit.,  I  (1885),  pp.  376-413. 

t  Compare  cases  on  p.  75  of  this  report. 


127 

which  by  careful  staining  the  nncolored  central  portion  is  easily  distinguished  from 
the  colored  periphery.  If  the  process  of  multiplication  is  very  rapid,  as  in  pigs  and 
rabbits,  the  organisms  do  not  attain  the  size  given  above,  but  divide  before  the  un- 
stained median  piece  becomes  distinctly  visible.  Under  these  circumstances  the  or- 
ganisms of  the  succeeding  generations  are  smaller,  only  one-half  as  large  as,  or  even 
smaller  than,  those  which  have  resulted  from  the  slow  division  of  the  bacteria.  The 
younger  generations  are  frequently  extraordinarily  small,  plainly  oval,  however,  and 
staining  uniformly  in  gentian  violet.  They  do  not  execute  any  spontaneous  move- 
ments. 

These  bacteria  were  fatal  to  mice,  rabbits,  and  guinea-pigs.  Pigeons 
succumbed  to  large  doses.  Fowls  and  rats  were  not  susceptible.  A 
comparison  of  the  virulence  of  these  bacteria  obtained  from  the  organs 
of  animals  at  the  four  different  times  indicated  above,  the  last  three 
being  from  the  same  locality,  shows  that  it  varied  slightly : 

1.  Rabbits  died  in  2  days,  mice  in  1  and  2  days  after  inoculation.     One  pig  4  to  5 
months  old,  which  had  received  subcntaneously  the  contents  of  two  Pravaz  syringes 
of  bouillon  culture  subcutaneously,  died  in  24  hours.    A  second  pig  treated  in  the 
same  way  died  in  48  hours. 

2.  Mice  died  in  24  hours. 

3.  Mice  died  in  24  hours;  rabbits  in  2  to  3 days;  guinea-pigs  in  4  to  8  days. 

4.  Mice  and  rabbits  died  in 24  hours ;    guinea-pigs  in  2  to 5  days;  one  pig,  which 
had  received  a  syringeful  of  a  bouillon  culture  into  each  lung,  died  in  2  to  3  days. 

The  lesions  ill  guinea-pigs,  rabbits,  and  mice  are,  in  the  main,  those 
obtained  with  the  bacteria  of  our  swine  plague.  The  above  table  indi- 
cates that  the  bacteria  from  the  last  lot  were  the  most  virulent,  as  they 
were  fatal  to  rabbits  in  24  hours. 

Through  the  kindness  of  Prof.  W.  H.  Welch,  of  the  Johns  Hopkins 
University,  a  culture  of  the  German  swine-plague  germ  was  obtained  iu 
1889,  and  a  second  fresh  culture  in  1890,  both  from  the  Berlin  Hygienic 
Institute.  Both  were  compared  with  the  American .  varieties  of  the 
swine-plague  bacteria.  While  the  bacteria  in  both  cultures  were  iden- 
tical in  form  and  biological  characters  with  the  swine-plague  bacteria 
of  this  country,  their  pathogenic  properties  varied  somewhat,  as  will 
be  seen  from  the  following  experiments: 

June  18, 1889.  From  the  original  agar  tube  agar  roll-cultnres  were  made,  and  from 
2  colonies  peptone-bouillon  cultures  prepared. 

June  25.  Two  rabbits  received  subcutaneously  one-eighth  and  one-sixteenth  cubic 
centimetre,  respectively,  2  mice  each  about  one-sixteenth  cubic  centimetre. 

June  26.  One  mouse  dead  this  morning.  Large,  dark  spleen,  fatty  liver.  No  bac- 
teria detected  in  cover-glass  preparations  from  blood,  spleen,  or  liver.  On  the  follow- 
ing day  a  few  colonies  had  appeared  in  the  agar  culture  from  spleen. 

June  27.  Second  mouse  dead.  Spleen  slightly  enlarged,  liver  fatty.  In  spleen  and 
tolood  very  many  swine-plague  bacteria,  exhibiting  the  polar  stain. 

Neither  of  the  rabbits  died.  The  one  which  had  received  one-eighth  cubic  centi- 
metre had  a  temperajtnre  of  106.4  °  F.  on  the  third  day.  The  temperature  of  the  other 
was  not  taken.  Both  were  killed  18  days  after  the  inoculation.  The  first  rabbitctn- 
siderably  emaciated.  On  the  inoculated  thigh  an  abscess  as  large  as  a  hen's  egg, 
discharging  from  an  opening  thick  pus.  The  suppuration  had  extended  to  the  abdo- 
men, where  over  6  square  inches  of  the  subcutis  was  infiltrated  with  pus  and  firmly 
adherent  to  abdominal  muscles.  la  the  second  rabbit  a  small  abscess  as  large  as  a 
*uarbJ»  on  inoculated  thigh.  Spleen  considerably  enlarged.  Foyer's  patches  swollen. 


128 

The  attenuated  condition  of  these  bacteria  discouraged  any  attempts 
to  determine  their  effect  upon  swine. 

The  second  culture  received  in  1890  proved  to  be  a  far  more  virulent 
type,  since  inoculation  of  rabbits  was  invariably  fatal  within  20  hours. 
These  bacteria  did  not  differ  therefore  in  this  respect  from  those 
obtained  from  outbreaks  VII  and  IX.  At  the  same  time  their  viru- 
lence was  still  greater,  as  will  appear  from  the  following  trials  upon 
swine : 

January  9,  1891.  Pig  No.  435,  black  male,  mixed  grade,  4£  months  old,  received 
subcutaneonsly  into  each  thigh  2-J  cubic  centimetres  of  a  peptone-bouillon  culture, 
or  5  cubic  centimetres  in  all.  Dies  just  24  hours  later. 

Pig  No.  437,  black  and  white  female,  4J  months  old,  one-half  cubic  centimetre  of 
the  same  culture  injected  into  a  vein  of  leg.  Animal  struggled  so  that  the  quantity 
injected  may  have  been  more  or  less  than  one-half  cubic  centimetre.  Dead  in  36 
hours. 

In  both  animals  there  was  considerable  necrosis  of  the  skin  and  O3clema  of  the  sub- 
cutis  where  the  inoculation  was  made.  These  animals  were  not  examined  until  post- 
mortem changes  had  appeared,  owing  to  other  work,  so  that  the  autopsy  notes  are 
omitted.  The  following  two  cases  are  of  interest  in  that  the  quantity  of  culture 
liquid  injected  was  smaller. 

February  11.  No.  460,  black  and  saudy  female,  3|  months  old,  weight  60  pounds, 
inoculated  subcutaneously  with  1  cubic  centimetre  of  a  bouillon  culture  24  hours  old, 
one-half  injected  into  each  thigh. 

No.  461,  animal  of  the  same  kind,  inoculated  in  the  same  manner  with  3  cubic 
centimetres. 

Both  were  found  unable  to  rise  on  the  following  morning  and  died  at  8  p.  m.,  about 
28  hours  after  inoculation. 

Autopsy  early  next  morning.  No.  461  in  good  condition.  C?eneral  blush  of  skin 
on  ventral  aspect  of  body  and  limbs.  Slight  reddening  of  subcutaneous  fat.  On 
both  inoculated  thighs  the  connective  tissue  reddened  and  all  minute  vessels  injected. 
On  the  right  the  connective  tissue  has  also  a  glistening  cedematous  appearance  which 
extends  upon  abdomen  as  far  as  umbilicus. 

Considerable  blood  extravasation  on  pericardium  and  on  epicardium  along  the 
base  of  the  heart,  interventricular  grooves  and  left  ventricle.  Veins  on  the  surface 
of  the  heart  distended.  In  right  side  a  very  dark,  soft  clot  imbedded  in  thick,  tarry 
blood.  Lungs  normal.  Intestines  have  a  uniformly  reddened  appearance  from  the 
outside.  Stomach  about  half  full  of  food.  Mucosa  of  fundus  hypersemic.  Mncosa 
of  small  intestine  normal.  In  large  intestine  much  dry  feces.  Mucosa  of  caecum  and 
colon  of  a  wine-red  color.  Liver  somewhat  flabby.  The  surface  has  a  mottled  ap- 
pearance due  to  the  varying  hyperaemia  of  the  lobules.  In  the  gall-bladder  a  firm 
body  which  almost  fills  it  out  and  has  the  appearance  of  beeswax.  The  body  is 
readily  crushed  with  the  fingers.  Surrounding  this  body  is  a  yellowish- white,  pasty 
mass.  Kidneys  hyperaemic. 

In  cover-glass  preparations  of  blood  and  kidneys  many  bacteria  exhibiting  the 
polar  stain  ;  in  liver,  only  a  few.  On  inclined  agar  traces  from  blood,  kidney,  and 
liver  transferred  with  wire  gave  rise  to  a  very  dense  growth  of  swine-plague  bac- 
teria. 

No.  460.  From  the  cut  ends  of  the  subcutaneous  veins  thick,  dark  blood  exudes. 
Skin  and  subcutis  as  in  No.  461,  the  vascular  injection  on  the  thighs  more  pro- 
nounced. 

Intestines  and  stomach  appear  much  reddened  from  the  outside.  On  the  abdominal 
walls  and  coils  of  large  intestine  are  little  lumps  of  yellowish-white  exudate.  A  few 
coils  of  the  small  intestine  where  they  touch  each  other  show  bands  of  petechiic  un- 
der serosa. 


129 

Condition  of  heart  as  in  461.  The  right  ventral  lobe  of  lungs  fastened  to  pericar- 
dium by  two  old  adhesions.  Somesubpleural  hemorrhages  on  principal  lobes.  Slight 
roughening  of  pleura  over  the  ventral  half  of  both  lungs.  Parenchyma  normal. 

Mucosa  of  fundus  of  stomach  over  an  area  6  inches  in  diameter  much  reddened, 
the  hypenumia  extending  to  subinueosa.  Small  intestine  contains  occasional  patches 
of  congested  mucosa.  In  the  large  intestine  hypenumia  slight  compared  with  461. 
Kidneys  and  liver  as  in  461. 

In  the  blood  many  swine-plague  bacteria.  Cultures  therefrom  and  from  kidneys 
confirmatory. 

It  should  be  noted  that  while  these  German  swine-plague  bacteria 
were  fatal  after  subcutaneous  inoculation,  the  only  cultures  of  the 
American  variety  which  killed  swine  after  such  inoculation  were  from 
outbreaks  I,  II,  and  IX.  Even  the  bacteria  from  the  latter  outbreak, 
virulent  as  they  were,  failed  in  this  respect  in  all  but  one  case.* 

Additional  investigations  concerning  Schiceineseuche  were  made  by 
Bleisch  and  Fiedelert  in  1888-'89.  The  disease  appeared  in  September 
on  a  dairy  farm,  evidently  introduced  by  recently  purchased  animals. 
It  spread  among  the  swine  in  several  different  stables,  even  among 
those  which  did  not  come  in  direct  contact  with  the  purchased  animals, 
but  were  simply  placed  in  the  pens  evacuated  by  the  latter.  Even  after 
the  disinfection  of  two  stables  the  animals  put  into  them  contracted  the 
disease.  The  investigations  were  continued  until  February,  1889,  and 
in  all  fifty-two  animals  were  examined.  The  disease  had  been  compar- 
atively mild  and  chronic ;  none  of  the  infected  died,  and  the  lesions  were 
observed  in  the  slaughtered  animals. 

During  life  the  symptoms  consisted  of  coughing,  which  increased  in 
severity  when  fresh  air  entered  the  stables,  difficult  breathing,  loss  of 
appetite,  and  emaciation.  The  temperature  fluctuated  between  102° 
and  105°  F.  The  lesions  observed  in  the  butchered  animals  were  in 
the  main  limited  to  the  thoracic  organs.  The  anterior  (or  cephalic) 
lobes  were  involved  in  grayish-red  hepatization,  which  in  more  ad- 
vanced cases  invaded  the  middle  and  posterior  (ventral  and  principal) 
lobes,  the  latter  only  in  isolated  regions.  The  bronchus  always  formed 
the  central  point  of  the  hepatization.  As  the  disease  progressed  par. 
tial  caseation  of  the  hepatized  tissue  and  of  the  bronchial  glands  took 
place.  The  caseous  masses  did  not  contain  tubercle  bacilli.  Pleuritis 
was  found  only  in  advanced  cases,  pericarditis  still  more  rarely. 

The  authors  found  in  practically  all  cases  bacteria,  which  they 
identify  with  the  bacteria  of  Schweineseuche  or  swine  plague.  They 
were  obtained  both  by  inoculating  rabbits  and  fowls  with  particles  of 
lung  tissue,  and  more  rarely  on  plate  cultures  from  the  lung  tissue 
directly.  The  bacteria  obtained  are  so  far  as  the  description  goes 
identical  morphologically  with  the  bacteria  found  by  Loftier,  Schiitz, 
and  others.  Their  effect  on  rabbits  differs  in  some  respects  from  the 
disease  produced  by  the  swine-plague  bacteria  proper.  The  disease 

*  See  p.  74. 

t  Zeitschrift  f.  Hygiene,  vi  (1889),  S.  401-452. 

3,614 9 


130 

may  last  from  2  to  13  days.  An  examination  of  the  text  shows 
that  some  rabbits  lived  longer,  one  27  days.  At  the  point  of  inocula- 
tion there  is  more  or  less  subcutaneous  purulent  infiltration  with  puru- 
lent lymphangitis.  The  liver  contained  in  many  cases  embolic  foci, 
which  are  described  (p.  406)  as  partly  branched,  partly  yellowish-white 
spots  found  on  the  surface  and  on  section,  and  consisting  of  a  pasty 
mass.  A  careful  examination  of  the  text  fails  to  convince  me  that 
these  embolic  foci  had  any  connection  with  the  disease.  Their  descrip- 
tion suggests  very  strongly  cysts  ofcoccidium  oviforme  in  various  stages 
of  enlargement.  Thus  a  rabbit  which  died  in  24  hours  from  an  iutratho- 
racic  inoculation  of  these  swine- plague  bacteria  showed  at  the  autopsy 
"the  liver  very  large,  the  surface  studded  with  numerous,  projecting, 
yellowish  nodules  as  large  as  pease,  similarly  the  cut  surface."  The 
coccidia,  if  such  they  may  have  been,  are  easily  overlooked  in  cover- 
glass  preparations,  for  the  method  of  preparation  and  staining  de- 
stroys them  pretty  thoroughly.  Moreover,  these  embolic  foci  do  not, 
according  to  their  report,  appear  with  any  regularity  in  the  inoculated 
animals. 

Another  point  to  be  noted  in  the  lesions  of  inoculated  rabbits  is  the 
absence  of  exudative  peritonitis  or  pleuritis,  which  is  a  very  constant 
lesion  in  rabbits  inoculated  with  the  American  races  of  swine  plague 
bacteria  when  they  live  more  than  two  days  after  inoculation. 

While  swine-plague  bacteria  have  little  or  no  effect  upon  fowls  unless 
large  doses  are  injected  into  the  muscles,  the  variety  under  discussion 
was  virulent  enough  to  prove  fatal  to  almost  all  fowls  inoculated. 
Death  occurred  from  one  day  to  several  weeks  after  inoculation.  In  one 
of  these  "  liver  emboli "  were  observed.  One  pig  which  had  received  a 
Pravaz  syringe  full  of  bouillon  culture  of  these  bacteria  died  in  ten 
hours.  The  lesions  observed  were  pleuritic  effusion,  hepatization  of 
almost  the  whole  of  the  right  lung.  In  the  left  there  were  isolated 
masses  of  hepatization.  A  second  pig  which  received  a  subcutaneous 
injection  had  a  slightly  elevated  temperature  for  several  days,  but  it 
recovered  subsequently. 

In  several  diseased  pigs  there  were  found  ulcers  on  the  surface  of  the 
body.  In  one  a  series  of  caseous  cysts,  starting  from  the  castration 
wound  and  extending  along  the  subperitoneal  tissue  as  far  as  the  um- 
bilicus, was  observed.  The  relation  of  these  lesions  to  the  disease  is, 
of  course,  not  determinable. 

The  authors,  after  having  determined  the  cause  of  the  disease,  en- 
deavored to  find  out  how  the  bacteria  are  transmitted  from  one  animal 
to  another.  The  swine  examined  belonged  to  one  farm  and  were  fed 
chiefly  with  sour  whey.  In  this  whey,  taken  from  the  troughs,  bacteria 
probably  identical  with  the  disease  germs  were  found  on  two  different 
occasions.  Further  investigation  revealed  the  fact  that  while  fresh 
milk  is  not  a  good  soil  for  these  bacteria,  sour  whey  is  very  favorable 
to  their  multiplication.  The  authors  therefore  explain  the  transmission 


131 

of  the  disease  by  assuming  that  in  the  common  feeding  trough  the  bac- 
teria are  mixed  with  the  milk.*  Some  of  this  accidentally  getting  into 
the  air  passages  during  feeding  introduces  the  disease  germs. 

This  brief  review  of  the  investigations  indicates  that  while  the  bac- 
teria found  by  Bleisch  and  Fiedeler  are  not  hog-cholera  bacilli  and  in 
general  the  same  as  swine-plague  bacteria,  there  are  some  minor  but 
constant  differences  to  which  attention  has  been  called.  It  is  a  curious 
fact  that  these  bacteria  were  attenuated  with  reference  to  rabbits,  but 
still  fatal  to  fowls.  Towards  the  varieties  described  in  this  report,  the 
fowl,  among  smaller  animals,  manifested  the  greatest  and  the  rabbit 
the  least  power  of  resistance.  It  is  not  improbable  that  attenuation,  as 
we  understand  the  term,  may  imply  a  decrease  of  virulence  as  to  one 
species  and  at  the  same  time  an  increase  as  to  others.  It  is  not  unreason- 
able to  assume  that  a  variety  of  swine-plague  bacteria,  apparently  atten- 
uated so  far  as  rabbits  are  concerne'd,  may  still  possess  virulent  proper- 
ties as  regards  more  refractory  animals.  The  properties  which  make  it 
feeble  to  rabbits  and  virulent  to  swine,  for  instance,  may  prove  different 
from  each  other.  It  is  only  by  such  assumption  that  we  can  understand 
the  action  of  swine-plague  bacteria  from  outbreak  I  and  II,  which, 
though  attenuated  with  reference  to  rabbits,  were  fatal  to  swine. 

A  very  interesting  communication  on  the  subject  of  swine  diseases 
in  Germany  was  recently  made  by  F.  Peters,  of  Schwerin.t  During 
the  winter  of  1887-'88  this  author  examined  cases  of  a  disease  among 
swine  which  strongly  suggests  hog  cholera.  The  disease  is  described 
in  brief  as  follows : 

Soon  after  the  sucking  period  is  completed,  the  young  pigs  lose  their 
desire  for  food  and  become  emaciated.  Cough,  increased  respiration, 
paleness  of  the  mucous  membranes,  and  diarrhea  are  also  observed. 
Towards  the  fatal  close  of  the  disease,  which  lasts  from  3  to  6  weeks, 
the  skin  of  the  ears,  the  neck,  and  chest  becomes  reddened.  The  greater 
number  of  those  attacked  die.  In  four  cases,  the  large  intestine  only 
was  affected.  The  description  given  corresponds  closely  with  the  vari- 
ous forms  of  necrosis,  softening  and  induration  commonly  called  ulcers 
in  hog  cholera  for  the  sake  of  simplicity.  In  a  fifth  case,  in  addition  to 
the  intestinal  changes,  there  were  found  recent  hepatization  of  the  left 
lung  and  exudative  pleuritis. 

The  author  made  some  bacteriological  examinations,  but  they  were 
not  thorough  enough  to  furnish  any  reliable  information  concerning  the 
character  of  the  bacteria  found.  While  he  maintains  that  they  are 
swine-plague  bacteria  the  description  he  gives  would  equally  apply,  as  far 
as  it  goes,  to  hog-cholera  bacilli.  As  the  territory  of  Schwerin  is  not 
very  far  from  Denmark,  the  scene  of  swine  pest  (hog  cholera)  during 
1887  and  since  that  time,  it  is  not  improbable  that  this  region  is  slowly 
being  invaded  by  two  diseases,  the  Schweineseuche,  or  swine  plague, 

*  The  American  varieties  of  swine-plague  bacteria  refuse  to  grow  in  acid  media, 
t  Die  Schweineseuche.    Archiv  f.  Thierheilkuude,  1890,  xvi,  S.  64. 


132 

found  by  Schiitz  in  1885,  and  the  swine  pest,  or  hog  cholera,  first  noticed 
in  Sweden  and  Denmark  in  1887.*  This  possibility  has  been  suggested 
recently  by  Bunzl-Federn  t  in  an  article  devoted  to  swine-plague  and 
closely  related  bacteria.  The  problem  of  infectious  swine  diseases 
would  then  enter  the  phase  in  which  the  investigations  of  this  Bureau 
found  it  as  far  back  as  1886  in  this  country,  in  which  a  mixture  of  two 
diseases  is  encountered  more  frequently  than  either  disease  by  itself. 

In  this  summary  some  articles  of  minor  importance  have  remained 
unnoticed.  Likewise  the  observations  of  Eoloff }  011  caseous  changes 
in  the  intestines  of  young  pigs  have  been  passed  by  because  they  give 
us  no  information  as  to  the  nature  of  the  bacteria  involved  in  the 
disease.  The  views  of  some  that  his  cases  were  swine  plague,  of  others 
that  they  may  have  been  hog  cholera,  are  purely  hypothetical. 

*  See  Special  Eeport  on  Hog  Cholera,  1889,  p.  181. 
t  Archiv  f.  Hygiene,  xil,  1891,  S.  198. 

t  Die  Schwindsucht,  fettige  Degeneration,  Scrophuloae  und  Tuberkulose  bei 
Schweinen.  Berlin,  1875, 


SOME  PRACTICAL  OBSERVATIONS  ON  THE  PREVENTION  OF 

SWINE  PLAGUE. 

1.  CONDITIONS  WHICH  MAY  FAVOR  AND  OPPOSE  OUTBREAKS  OF  SWINE 

DISEASE. 

The  factors  which  enter  into  the  production  of  outbreaks  of  swiiie 
plague  may  be  divided  for  convenience  into  two  classes,  those  pertaining 
to  the  animal  itself,  and  which  make  it  more  or  less  susceptible  or  insus- 
ceptible to  the  specific  bacteria,  and  those  which  relate  to  the  bacteria. 

The  conditions  which  make  animals  more  susceptible  to  infection  are 
as  varied  as  the  conditions  which  reduce  their  vitality.  The  importance 
of  rearing  and  keeping  animals  in  such  a  manner  as  to  produce  and 
maintain  a  healthy  action  of  the  various  functions  of  the  body  has  not 
been  insisted  upon  with  as  much  emphasis  as  it  deserves,  owing  to  the 
somewhat  overshadowing  influence  which  the  study  of  pathogenic 
bacteria  has  exerted  upon  all  minds.  It  is  evident,  however,  that  vet- 
erinary hygiene  has  much  to  do  with  the  decline  of  large  epizootics,  not 
only  by  keeping  away  the  germs  of  disease,  but  by  enabling  the  animal 
body  to  resist  their  attack^.  Of  those  conditions  of  swine  which  invite 
disease  very  little  is  as  yet  positively  known,  and  we  simply  call  atten- 
tion to  a  few  to  arouse  the  interest  of  those  who  are  in  position  to  make 
observations. 

There  have  been  indications  during  the  course  of  experiments  at  the 
Bureau  Station  that  the  breed  may  have  some  influence  in  predisposing 
to  infection.  As  an  illustration  we  may  cite  an  experiment  in  vaccina- 
tion of  swine  against  hog  cholera  carried  on  at  the  Station  in  1889-'90.* 
The  vaccination,  which  consisted  in  subcutaneous  inoculation  of  culture 
liquid,  seems  to  have  had  no  effect ;  for,  when  the  time  for  exposure  came, 
practically  all  pigs  from  one  lot  succumbed  and  all  from  another  lot 
survived.  The  latter  were  Essex  grades  reared  in  pens;  the  former, 
grades  of  mixed  Jersey  Reds  and  Chester  Whites  not  raised  in  pens. 
While  it  is  impossible  to  give  any  facts  as  to  the  relative  resistance  of 
different  breeds  to  swine  diseases,  it  is  a  subject  which  should  receive 
the  due  consideration  of  swine-breeders,  especially  in  those  States 
where  swine  diseases  are  more  or  less  stationary. 

Age  is  another  important  element.  We  have  found  a  decided  differ- 
ence in  the  susceptibility  to  both  hog  cholera  and  swine  plague  in  favor 
of  older  swine.  This  element  of  age  is  familiar  to  all  with  reference  to 


Report  of  the  Secretary  of  Agriculture  for  1890,  p.  110. 

133 


134 

certain  human  maladies,  such  as  scarlet  fever,  measles,  diphtheria,  and 
some  other  diseases  which  preferably  attack  the  young. 

Feeding  is  perhaps  the  most  important  factor  in  predisposing  swine 
to  disease.  The  assimilation  of  large  quantities  of  food  and  its  con- 
version into  fat  seems  to  be  the  one  essential  function  of  swine.  This 
goes  on  to  such  a  degree  as  to  lead  to  pathological  conditions  after  a  time. 
Not  only  the  ingestioii  of  large  quantities  of  food,  but  of  one  kind  for  a 
long  time,  is  in  itself  opposed  to  the  habits  of  such  omnivorous  animals. 
Besides  overfeeding  upon  one  kind  of  food  we  have  the  uncleanly  sur- 
roundings in  which  swine  are  apt  to  be  kept  contributing  materially  to 
a  reduction  of  vitality. 

In  addition  to  the  unhealthful  modes  of  existence  to  which  swine  are 
subjected,  and  partly  springing  from  them,  are  certain  pathological  con- 
ditions induced  by  parasites  of  different  kinds.  The  life  history  of  some 
of  the  more  important  parasites  infesting  swine  is  still  to  be  elucidated. 
As  a  rule,  we  have  found  in  our  post-mortem  examinations  a  larger 
Dumber  and  variety  of  internal  parasites  in  those  herds  which  have 
been  allowed  to  run  freely  than  in  those  brought  up  in  pens.  The  op- 
portunities for  infection  seem  to  be  much  greater  in  the  former  case 
than  in  the  latter. 

As  to  the  damage  done  by  parasites  it  is  difficult  to  form  an  accurate 
estimate  from  ordinary  observation.  Obvious  damage  may  be  done  in 
the  air  passages  by  lung  worms  (strongylus  paradoxus)  and  in  the  small 
intestine  by  ascaris  and  echinorhynchus.  The  lung  worms  may  be 
met  with  in  all  seasons  of  the  year  in  swine  up  to  3  mouths  old.  They 
invariably  inhabit  the  terminal  portion  of  tfie  two  large  bronchi  of  the 
principal  lobes.  Here  there  is  generally  a  partial  or  total  occlusion 
of  the  bronchus  for  1  or  2  inches  from  the  caudal  border  of  the  lobe, 
due  to  the  lung  worms  and  the  enveloping  mucus.  In  some  cases  tho 
occlusion  is  followed  by  collapse  and  broncho-pneumonia  of  the  lobes 
supplied  by  the  bronchus  and  its  branches.  The  hepatized  lung  tissue 
assumes  a  bright  or  pale  red  color.  When  the  lung  worms  are  very 
abundant  larger  branches  of  the  same  bronchus  become  filled  with 
these  parasites  and  the  broncho-pneumonia  may  extend  over  a  greater 
portion  of  the  principal  lobes.  That  lungs  in  this  condition  are  more 
susceptible  to  the  invasion  of  swine-plague  bacteria  will  be  generally 
admitted.  The  bronchitis  begun  where  the  lung  worms  mature  may 
extend  after  a  time  into  the  other  air  tubes.  In  outbreaks  VII  and 
VIII  lung  worms  were  found  in  almost  every  animal  examined. 

Another  question  arises  with  reference  to  lung  worms  as  the  possible 
bearers  of  the  bacteria  into  the  lungs.  This  will  not  be  answered  until 
more  is  known  of  the  life  history  of  these  parasites.  Meanwhile  the 
evidence  would  hardly  support  the  opinion  that  they  may  introduce  the 
virus.  The  pneumonia  usually  begins  in  the  small  ventral  lobes  and 
travels  from  them  while  the  lung  worms  begin  their  injurious  work  in 
the  principal  lobes  farthest  removed  from  the  ventral  lobes.  All  that 


135 

can  be  said  is  that  they  may  make  the  lungs  more  susceptible  to  the 
disease. 

In  the  intestines  ascarides  are  not  infrequently  found  extending  into 
the  common  bile  duct  from  the  duodenum.  Some  even  enter  the  gall- 
bladder, while  others  imbed  themselves  in  the  ducts  coming  from  the 
various  lobes  of  the  liver  and  completely  obstruct  the  flow  of  bile.  The 
echinorhynchus  is  well  known  as  attaching  itself  to  the  mucous  mem- 
brane of  the  small  intestine,  and  producing  ulcerous  depressions  simu- 
lating those  of  hog  cholera. 

That  there  may  be  other  predisposing  causes  at  certain  seasons  of 
the  year,  such  as  obscure  malarial  diseases  due  to  protozoa,  the  inva- 
sion of  the  muscular  system  by  psorospermia,  trichina1,,  etc.,  need  simply 
to  be  mentioned,  since  no  positive  evidence  is  at  hand. 

The  important  factor  in  the  production  of  swine  plague  (and  hog 
cholera  as  well)  bearing  on  the  bacteria  is  their  virulence.  We  have 
seen  in  the  chapter  on  the  pathogenic  action  of  swine-plague  bacteria 
that  their  virulence  or  disease-producing  power  is  subject  to  consider- 
able variation,  and  that  they  may  be  very  virulent  as  obtained  from  one 
outbreak  and  much  less  so  from  another.  It  may  be  laid  down  as  a 
general  rule  that  the  more  virulent  the  bacteria  the  more  severe  the 
resulting  epizootic,  and  the  greater  the  mortality.  While  a  more  attenu- 
ated variety  of  bacteria  may  spare  the  older  and  more  hardy  animals 
of  a  herd,  these  will  succumb  to  a  more  virulent  variety.  Just  here 
the  facts  presented  under  the  preceding  head  show  their  importance. 
Attenuated  or  weaker  varieties  of  swine  plague  may  attack  the  young 
and  the  badly  kept  swine* those  infested  with  parasites  and  those  of 
poorer  breeds,  while  the  stronger  may  not  become  diseased.  This  may 
explain  also  why  some  herds  of  swine  are  destroyed  and  neighboring 
ones  escape,  although  both  may  have  had  the  same  opportunities  of 
infection. 

The  appearance  of  an  epizootic  depends  thus  upon  the  condition  of 
the  herd  and  the  relative  virulence  of  the  bacteria.  While  there  are 
bacteria  whose  virulence  is  sufficient  to  sweep  away  every  obstacle,  we 
are  convinced  also  that  much  disease  due  to  attenuated  bacteria  could 
be  counteracted  by  a  more  hygienic  breeding  and  rearing  of  swine. 

2.    THE    DISTRIBUTION    AND    TRANSMISSION    OF    SWINE-PLAGUE    BAC- 
TERIA. 

We  have  seen  in  preceding  pages  that  besides  the  particular  herd  in 
which  swine  plague  exists  as  an  epizootic,  bacteria  not  distinguishable 
from  those  of  swine  plague  are  found  widely  distributed  in  the  air  pas- 
sages of  healthy  swine,  and  of  other  domesticated  animals,  such  as 
cattle,  dogs,  and  cats.  Are  these  bacteria  capable  of  producing  disease 
in  -swine  at  any  time  and  therefore  a  continual  source  of  danger,  or  are 
they  harmless  ?  This  question  can  not  be  answered  definitely  in  the 
present  state  of  knowledge  on  this  subject.  As  a  rule,  the  bacteria 


136 

found  in  healthy  animals  belong  to  more  or  less  attenuated  varieties  and 
are  most  likely  incapable  of  producing  disease  excepting  when  the  con- 
dition of  the  animals  is  very  poor.  Sporadic  disease  in  such  debilitated 
animals  is  not  contagious  and  does  not  spread  to  other  animals  of  the 
herd  unless  all  are  in  equally  reduced  condition.  It  may  happen,  how- 
ever, that  such  swine  plague  bacteria,  which  live  in  the  air  passages  of 
older  swine  as  survivals  of  former  exposure  and  disease,  may  become 
dangerous  to  young  pigs.  Of  this  possibility  outbreak  VIII  may  serve 
as  an  illustration.  The  litter  of  young  pigs  died  of  swine  plague 
caused  by  a  considerably  attenuated  variety  of  bacteria,  such  as  may 
be  found  in  apparently  healthy  swine  of  greater  age.  It  should  also 
be  remembered  that  even  older  swine,  which  have  been  through  the 
fattening  process  and  are,  commercially  speaking,  in  the  best  condition, 
are  really  in  an  abnormal  or  a  pathological  state,  and,  therefore,  may 
be  more  or  less  susceptible  to  infection. 

We  have  shown  that  there  are  herds  of  swine  from  certain  farms  en- 
tirely free  from  pathogenic  bacteria,  and  the  question  arises,  What  is  the 
source  of  those  swine  plague-like  bacteria  found  in  the  upper  air  pas- 
sages of  many  herds?  I  am  inclined  to  think  that  they  are  transmitted 
from  older  swine  to  younger  ones,  producing  disease  only  under  aggra- 
vated conditions  in  isolated  cases,  which  disease  does  not  spread  to 
other  animals. 

When  we  come  to  the  more  virulent  varieties,  those  for  example, 
which  destroy  rabbits  within  16  hours  after  inoculation,  the  case  is 
entirely  different.  Their  presence  is  probably  never  manifested  ex- 
cepting by  disease,  and  it  is  against  the  introduction  of  these  bacteria 
that  the  swine-breeder  must  protect  himself.  Such  bacteria  always 
come  from  some  outbreak  of  disease  directly  or  indirectly.  Let  us  con- 
sider briefly  through  what  agencies  such  bacteria  may  be  introduced 
into  a  herd. 

In  the  report  on  hog  cholera  and  in  the  present  volume  it  was  pointed 
out  that  swine-plague  bacteria  are  far  less  hardy  than  hog-cholera 
bacilli.*  The  former  perish  rapidly  in  water  and  in  liquids  unsuited  to 
their  multiplication.  They  survive  drying  for  a  few  days  only.  In  gen- 
eral, they  speedily  disappear  after  they  have  left  the  body  of  diseased 
swine,  and  it  is  highly  doubtful  whether  they  would  survive  a  month  in 
the  soil  or  in  pens.  Such  agencies  as  streams,  manure,  etc.,  which  may 
distribute  hog-cholera  bacilli  over  considerable  distances  are  of  re- 
stricted importance  in  swine  plague.  The  chief  danger  lies  in  contact 
with  diseased  or  infected  swine.  Intermediate  carriers  of  infection  can 
only  act  for  a  short  time,  while  swine  may  harbor  disease  germs  for 
months  in  localized  inflammations,  such  as  abscesses  under  the  skin  and 
in  the  joints,  and  it  is  possible  that  they  may  vegetate  on  the  mucous 
membranes  of  the  air  passages  much  longer. 

*  See  table,  p.  92. 


137 

Swine  must  thus  be  regarded  as  the  chief  vehicle  of  infection.  This 
maybe  conveyed  directly  from  diseased  to  healthy  animals;  it  may  be 
conveyed  by  those  which  have  passed  through  the  disease,  and  hence 
by  older  to  younger  swine.  It  is  safe  to  assume  that  any  swine  which 
have  at  any  time  been  exposed  to  swine  plague  (or  hog  cholera)  are 
liable  to  convey  the  disease,  because  we  do  not  know  when  the  specific 
disease  germs  leave  the  body. 

Other  sources  of  danger  are  railroads  leaving  fresh  manure  in  differ- 
ent places,  the  vicinity  of  slaughter-houses,  rendering  establishments, 
or  any  places  where  the  viscera  of  swine  may  be  scattered  or  where 
numbers  of  living  swine  are  temporarily  housed.  If  we  bear  in  mind 
the  wide  distribution  of  infectious  swine  diseases  it  is  easy  to  believe 
that  in  any  large  herd  of  swine  collected  from  different  localities  there 
are  always  some  diseased  or  infected.  It  is  essential,  therefore,  in 
guarding  against  disease,  to  look  with  suspicion  upon  all  swine  the 
history  of  which  is  not  known  to  some  extent  at  least. 

There  is  a  practice  current  in  some  parts  of  the  country,  and  well 
illustrated  by  the  history  of  outbreak  IX,  of  gathering  together  herds 
of  young  pigs  from  various  localities  through  the  intervention  of  deal- 
ers. In  regions  where  swine  diseases  are  prevalent  much  of  the  time, 
and  where  the  virus  never  dies  out,  this  is  a  specially  dangerous  practice. 
While  swine  may  not  be  visibly  diseased,  or  may  simply  appear  some- 
what unthrifty,  they  still  may  carry  the  seeds  of  a  virulent  outbreak 
within  them  which  need  a  little  time  to  gain  the  required  momentum. 
The  mild  character  of  a  disease  in  any  one  animal  is  no  evidence  of  the 
character  of  the  germ.  For  this  mildness  may  be  due  to  a  very  viru- 
lent germ  acting  upon  a  highly  insusceptible  animal  and  causing  a 
more  prolonged  chronic  disease.  In  fact,  these  partly  insusceptible  ani- 
mals are  the  most  likely  to  appear  in  the  markets  because  they  are  the 
remnants  of  herds  destroyed  by  disease.  We  have  frequently  been  able 
to  demonstrate  by  experimental  inoculations  the  general  accuracy  of 
these  statements.  Thus  bacteria  obtained  from  inoculated  cases  which 
had  assumed  a  more  chronic  course  had  not  lost  any  of  their  virulence. 
In  experiments  bearing  on  vaccination  we  have  been  able  to  increase 
the  insusceptibility  of  rabbits  and  guinea-pigs  so  that  virulent  bacteria 
produced  only  a  mild  form  of  the  disease,  prolonged  from  days  to  weeks 
and  even  mouths.  Yet  the  bacteria  cultivated  from  such  cases  and  in- 
jected into  animals  not  vaccinated  showed  no  loss  of  virulence.  Again, 
we  have  found  swine-plague  bacteria  in  apparently  healthy  swine  inocu- 
lated two  months  previously,  and  in  case  of  hog  cholera  we  have  found 
the  bacilli  in  the  organs  of  swine  6  to  7  months  after  apparently  un- 
successful inoculations.  These  bacteria  possessed  the  original  viru- 
lence. 

The  question  has  frequently  arisen  in  the  course  of  these  investiga- 
tions whether  the  bacteria  are  ever  introduced  into  herds  in  the  food. 
This  involves  another  question,  whether  hog-cholera  or  swine-plague 


138 

bacteria  do  exist  independently  of  diseased  or  healthy  animals.  As  to 
both  kinds  of  disease  germs  there  is  no  evidence  that  they  live  outside 
of  the  animal  organism,  except  temporarily,  and  that  if  the  food  happens 
to  be  infected  the  infection  has  come  from  animals  directly  or  indirectly, 
and  that  it  is  simply  a  question  of  time  whether  such  infection  is  still  in 
a  living  condition  or  not.  Food,  however,  may  be  infected  with  other 
pathogenic  bacteria  which  may  become  dangerous  in  producing  second- 
ary and  perhaps  fatal  lesions  in  animals  already  diseased.  This  applies 
more  directly  to  the  swill  food  which  is  used  by  many  in  the  vicinity  of 
large  cities  and  which  is  composed  of  such  miscellaneous  material  partly 
in  a  condition  of  fermentation  and  decomposition  that  the  presence  of 
disease  germs  may  be  considered  probable  at  any  time.  In  outbreak 
IX,  in  which  swill  food  was  mainly  used,  the  bacilli  of  malignant  O3deina 
were  obtained  from  some  cases  and  very  likely  added  to  the  fatality  of 
the  outbreak. 

3.  THE  RELATION  OF  HOG  CHOLERA  TO  SWINE  PLAGUE.* 

Throughout  this  report  frequent  reference  has  been  made  to  hog 
cholera  because  many  outbreaks  studied  during  the  past  five  or  six 
years  were  mixtures  of  both  diseases,  and  it  is  therefore  difficult  to  sep- 
arate them  in  order  to  estimate  correctly  the  damage  done  by  each. 
We  have  encountered  a  small  number  of  outbreaks,  of  which  some  were 
due  to  hog  cholera,  others  to  swine  plague,  but  the  majority  were  the 
result  of  a  mixed  infection. 

The  outbreaks  of  hog  cholera  not  complicated  with  swine  plague  were 
generally  of  a  virulent  type.  When  both  diseases  showed  themselves, 
neither  was,  as  a  rule,  of  any  great  virulence.  To  explain  the  frequent 
intermingling  of  these  diseases  we  must  refer  to  the  bacteriological  re- 
sults of  the  past  few  years.  Besides  the  virulent  varieties  of  hog-chol- 
era bacilli,  which  produce  a  characteristic  fatal  disease  in  rabbits  after 
subcutaneous  inoculation  of  exceedingly  minute  doses,  we  have  encoun- 
tered about  half  a  dozen  varieties  whose  virulence  was  much  diminished. 
The  diminishing  pathogenic  power  is  shown  by  the  absence  of  a  fatal 
disease  after  subcutaneous  inoculation  of  rabbits,  and  even  small  quan- 
tities of  culture  liquid  injected  into  the  circulation  may  produce  only  a 
mild  disease.  In  onet  there  seemed  to  be  no  virulence  left,  and  it 
becomes  questionable  whether  such  bacilli  can  be  regarded  as  hog- 
cholera  bacilli  at  all.  The  attenuated  bacilli  have  likewise  very  little 
or  no  effect  on  swine. 

Parallel  to  this  diminishing  scale  of  virulence  of  hog-cholera  bacilli, 
we  have  a  similar  scale  among  swine-plague  bacteria  repeatedly  set 
forth  in  the  preceding  pages.  On  the  one  hand,  some  varieties  will 
destroy  rabbits  within  10  hours  after  inoculation  of  the  minutest  trace 
of  culture  material  into  the  skin ;  on  the  other  there  are  varieties 
which  barely  destroy  rabbits  after  large  doses  have  been  injected  directly 

*  See  also  pp.  102-108.  t  Bacillus  y,  outbreak  IX,  p.  78. 


139 

into  the  circulating  blood.  All  of  these  varieties  have  been  obtained 
from  the  internal  organs  of  diseased  swine,  and  hence  even  the  very  at- 
tenuated ones  may  have  had  some  share  in  the  disease. 

If  we  picture  to  ourselves  a  wide  distribution  of  these  several  varie- 
ties of  hog-cholera  and  swine-plague  bacteria  in  the  bodies  of  diseased 
and  of  partly  recovered  swine,  and,  in  case  of  swine-plague  varieties, 
in  the  air  passages  of  healthy  animals,  it  is  not  difficult  to  understand 
why  there  are  so  many  mixed  outbreaks.  The  practice  already  alluded 
to,  of  purchasing  pigs  from  many  herds  and  localities  and  bringing  them 
together  to  be  fattened  as  one  herd,  is  the  most  successful  method  of 
bringing  various  grades  of  pathogenic  bacteria  together  and  of  pro- 
ducing a  mingling  of  two  diseases.  These  mixed  outbreaks  may  de- 
velop in  other  ways  also.  The  disease  may  begin  as  hog  cholera  and 
become  subsequently  complicated  with  swine  plague  or  the  reverse 
may  be  true ;  the  disease  may  begin  as  swine  plague,  and  become  com- 
plicated with  hog  cholera.  In  either  case  the  most  virulent  variety 
will  probably  start  the  disease,  and  any  attenuated  hog-cholera  or  swine- 
plague  bacteria,  which  are  latent  in  some  of  the  animals  of  the  herd, 
or  have  not  yet  been  killed  out  of  the  soil,  and  the  surroundings  from 
a  former  outbreak  may  start  into  activity  and  thus  produce  a  more 
fatal  mixed  disease.  It  is  evident  that  such  secondary  attacks  of  atten- 
uated bacteria  would  not  take  place  if  the  animals  had  not  been  weak- 
ened by  the  primary  disease.  This  may  be  the  only  way  in  which  the 
great  majority  of  the  swine-plague  bacteria  in  the  air  passages  of 
healthy  animals  can  exert  any  pathogenic  effect  whatever.  It  is  like- 
wise difficult  to  understand  how  attenuated  hog-cholera  bacilli  can  act 
without  assistance  from  swine  plague.  These  statements  may  be  illus- 
trated by  referring  to  the  investigations.  Thus  in  outbreak  IV  the  dis- 
ease was  evidently  swine  plague  at  first,  and  complicated  with  hog- 
cholera  later.  For  the  hog-cholera  bacilli  were  only  observed  in  the  later 
cases.  It  should  likewise  be  borne  in  mind  that  in  swine  plague  some 
cases  are  usually  of  a  more  chronic  type.  The  disease  lasts  some  time 
and  is  associated  with  caseous  changes  in  the  lungs.  Any  hog-cholera 
bacilli  have  thus  abundant  opportunity  to  enter  the  weakened  organism 
and  appear  after  death  in  cultures  from  the  internal  organs.  For  the  same 
reason  hog-cholera  outbreaks  characterized  by  very  feeble  pathogenic 
activity  of  the  hog-cholera  bacilli,  and  hence  of  a  more  prolonged  dura- 
tion and  chronic  character,  are  usually  complicated  with  swine  plague, 
because  the  latter,  even  though  of  a  feeble  activity,  has  been  able  to  in- 
vade the  weakened  organism  and  has  had  time  to  do  so.  In  virulent 
outbreaks  of  either  disease  death  may  ensue  so  rapidly  that  no  invasion 
of  the  other  disease  takes  place.  These  statements  presuppose,  of 
course,  that  both  kinds  of  bacteria  exist  in  the  surroundings  of  the  herd. 

The  appearance  of  mixed  outbreaks  due  to  bacteria  brought  by  dif- 
ferent herds  is  suggested  by  outbreak  VII.  Even  after  a  very  thorough 
examination  of  Nos.  1  and  2  no  hog-cholera  bacilli  could  be  found.  In 
the  subsequent  cases  in  which  they  were  present,  they  were  readily  de- 


140 


tected  in  the  various  organs  examined.  Moreover  there  was  quite  a 
difference  observable  in  the  lesions  of  the  various  cases  corresponding- 
more  or  less  closely  to  the  nature  of  the  bacteria  found.  The  supposi- 
tion already  presented  in  regard  to  this  outbreak  was  that  the  hog-chol- 
era bacilli  were  either  present  in  the  locality  into  which  the  pigs  were 
brought  or  were  carried  by  some  one  or  more  pigs  in  the  herd. 

Hog  cholera  and  swine  plague  thus  mutually  assist  one  another  to 
produce  those  feebly  infectious,  chronic  diseases  which  are  common  at 
all  seasons  of  the  year,  and  it  is  not  unreasonable  to  suppose  that  from 
such  apparently  insignificant  diseases  large  epizootics  are  developed, 
which  by  a  gradual  return  of  virulence  in  the  bacteria,  and  under  slight 
provocations  of  forced  feeding,  cold,  or  other  debilitating  influences 
on  the  part  of  their  victims,  burst  forth  at  certain  seasons  of  the  year 
with  unexpected  violence.* 

This  condition  of  things  refers  more  particularly  to  localities  where 
swine-raising  has  been  conducted  on  a  large  scale,  where  these  dis- 
eases never  actually  die  out,  and  where  consequently  the  specific 
bacteria  are  always  on  hand.  In  those  regions  which  are  being  invaded 
by  these  plagues  anew  the  latter  may  smolder  for  several  years  by 
reason  of  the  introduction  of  attenuated  varieties  before  they  break 
out  as  genuine  epizootics. 

There  are  no  facts  at  hand  to  indicate  any  difference  in  the  distribu- 
tion of  these  two  plagues.  The  localities  where  either  one  or  both 
plagues  have  been  determined  by  bacteriological  investigations  may 
be  tabulated  as  follows : 


Locality. 

Character  of  plague. 

By  the  Bureau  of  Animal  Industry  : 

Hog  cholera. 
do  

Swiue  plaguo. 
Do. 
Do. 

Swino  plague. 
Do. 
Do. 
Do. 

Swino  plaguo. 
Do. 
(1) 
Swine  plaguo. 

Swine  plague. 
Do. 

Virginia,  various  outbreaks  1885-'90  

...do  

Nebraska  1886  

.  .  do  

Illinois  (Genoseo),  July,  1886    

Illinois  (Sodorus)   September  1886      ... 

Hog  cholera. 

Iowa,  December,  1886  

*(?) 
t<») 
(?) 
Hog  cholera. 
.  .  do  

New  Jersey  (Johnsonburgh),  October,  1887....  

New  Jersey  (Pleasantville).  July,  1890.....  

Missouri  (Chillicothe)    1890  '91        .... 

Nebraska  (1886-'88)   by  Billings       .            

Maryland  (Baltimore),  by  Welch  and  Clement       .                  ... 

..  do  

South  Carolina,  by  Bolton  

...  do  

Illinois,  by  Burrill  

Massachusetts  'near  Boston),  by  J.  A.  Jefl'ries  

*  The  investigation  in  Iowa  did  not  bring  to  light  any  hog-cholera  bacilli,  though  the  lesions  sug- 
gest, the  presence  of  attenuated  forms  not  accessible  by  the  usual  methods. 

tin  this  small  outbreak  bacilli  closely  resembling  those  of  hug  cholera  were  found  in  the  spleen. 
Their  virulence,  however,  was  very  feeble.  Subcutaneous  inoculation  had  no  effect  on  rabbits. 


*  A  curious  instance  of  this  recrudescence  of  apparently  enfeebled  virus  is  outbreak 
IV  referred  to  above.  During  February  and  March  swine  plague  from  a  neighboring 
farm  became  mingled  with  hog  cholera  in  an  infected  pen  on  the  Station  in  which  this 
disease  had  apparently  lost  all  virulence.  The  cases  of  mixed  disease  were  of  but 
slight  severity  so  far  as  hog  cholera  lesions  were  concerned.  Gradually  towards 
spring,  animals  placed  in  this  pen  died  rapidly  of  hcmorrhagic  hog  cholera.  There 
was  no  evidence  of  the  introduction  of  another  bacillus,  nor  were  any  changes  detected 
as  regards  the  bacteria  in  cultures  or  in  the  inoculated  rabbits. 


141 

4.   THE  RELATION  OF  SWINE  PLAGUE  TO  DISEASES  OF  OTHER  DOMES- 
TICATED ANIMALS. 

The  question  whether  the  different  species  of  domesticated  animals 
on  a  farm  may  take  from  or  transmit  to  swine  the  disease  which  we 
have  been  considering  is  of  very  great  importance  in  view  of  the  chang- 
ing conditions  of  live-stock  interests  which  are  going  on  in  different 
directions  in  various  parts  of  our  country. 

The  problem  may  be  stated  as  follows :  Has  the  bringing  together 
of  different  species  of  animals  for  the  purposes  of  feeding,  etc.,  on  the 
same  ground,  a  tendency  to  increase  disease  in  one  or  the  other  species  ? 
Will  swine  take  swine  plague  from  cattle  and  will  they  transmit  it  to 
sheep  and  horses,  for  example,  or  is  the  reverse  ever  observed  ? 

Investigations  and  observations  during  the  past  13  years  lend  some 
color  to  such  possibilities,  and  it  becomes  necessary  at  least  to  call  at- 
tention to  those  engaged  in  raising  and  keeping  farm  animals  to  what 
has  been  determined  in  this  direction,  and  to  arouse  their  interest  in 
the  investigation  of  outbreaks  of  swine  plague,  especially  as  regards 
the  immediate  causes. 

In  the  summer  of  1878  there  appeared  in  three  royal  game  preserves, 
in  the  vicinity  of  Munich  in  Bavaria,  a  very  fatal  epizootic  among  the 
wild  boars  and  deer,  of  which  234  boars  and  153  deer  perished.*  It 
was  also  noticed  that  even  after  the  plague  in  the  parks  had  apparently 
died  out,  disease  among  cattle  in  the  neighborhood  appeared,  and  this, 
according  to  the  observations  of  veterinarians,  was  identical  with  the 
disease  observed  among  the  game  in  the  parks. 

The  disease  was  very  acute,  lasting  from  12  to  36  hours  in  the  major- 
ity of  cases.  In  those  in  which  pneumonia  and  pleuritis  were  present  the 
disease  may  have  lasted  5  or  6  days.  The  chief  lesions  among  the  latter 
were  croupous  pneumonia,  pleuritis,  pericarditis,  and  uiediastiuitis. 
In  cattle  the  disease  appeared  in  two  forms.  In  one  a  swelling  was 
observed  on  the  head,  the  face,  the  neck,  or  in  the  tongue,  which  as- 
sumed enormous  proportions  in  6  to  12  hours  and  led  to  suffocation.  The 
swelling  was  due  to  serous  or  serous  and  hemorrhagic  infiltration.  In 
the  other  form,  in  addition  to  the  pneumonia,  pleuritis,  and  pericarditis 
observed  in  the  game,  there  was  always  present  a  severe  hemorrhagic 
inflammation  of  the  small  intestine.  Bellinger  called  these  forms  exan. 
thematic  and  pectoral,  respectively.  At  this  time  bacteriological  meth- 
ods were  still  undeveloped,  and  nothing  is  known  of  the  nature  of  the 
bacteria  causing  this  outbreak  save  the  fact  that  they  were  not  anthrax 
bacilli.  A  number  of  inoculations  were  made  upon  various  animals, 
which  testify  to  the  extreme  virulence  of  the  specific  bacteria. 

Rabbits  died  6  to  8  hours,  sheep  and  goats  30  to  36  hours  after  inocu- 
lation. Two  old  horses  died  after  subcutaneous  inoculation  with  blood 
from  cattle  in  a  very  short  time.  A  young  steer,  1£  years  old,  was  fed 

*  Pollinger.    Uber  erne  i^eue  Wild-  und  Rmderaencbe,    Miiuchen,  1878, 


142 

with  a  thimbleful  of  the  intestinal  contents  of  a  calf  which  had  suc- 
cumbed to  an  enormous  swelling.  The  steer  died  in  54  hours  with 
pneumonia  and  pleuritis.  A  pig  inoculated  subcutaueously  over  the 
left  shoulder  with  a  few  drops  of  blood  died  in  22  hours.  Besides  an 
extensive  erysipelatous  swelling  starting  from  the  point  of  inoculation 
there  was  beginning  flbrinous  pleuritis. 

The  disease  reappeared  in  the  following  years,  either  sporadically  or 
in  restricted  outbreaks.  In  1879  and  1880  it  was  observed  among 
domesticated  animals  alone ;  in  1881  among  the  animals  in  the  game 
preserves.  In  1885  Kitt*  published  some  investigations  which  were 
destined  to  throw  more  light  upon  this  new  plague.  With  blood  from 
an  outbreak  among  cattle  resembling  the  epizootic  described  by  Bolliu- 
ger,  Kitt  made  some  inoculations  upon  small  animals.  Of  mice,  rab- 
bits, guinea-pigs,  and  one  pigeon  inoculated,  the  mice  and  rabbits  died 
within  24  to  36  hours,  the  pigeon  in  36  hours.  The  guinea-pigs  were 
not  affected.  Lesions  were  in  general  absent.  The  blood  contained 
large  numbers  of  bacteria.  Subsequently  the  spleens  of  an  ox,  a  young 
pig  (of  which  eight  had  died),  and  a  horse  which  had  succumbed  in  the 
same  locality,  showed  on  microscopic  examination  the  same  bacteria, 
whose  virulence  tested  on  rabbits  was  likewise  the  same.  In  a  cow  in- 
oculated subcutaneously  over  the  left  shoulder  an  extensive  inflamma- 
tory oedema  of  the  inoculated  shoulder  appeared,  which  extended  over 
the  entire  left  limb.  The  swelling  later  became  converted  into  an 
abscess,  but  the  animal  did  not  die. 

Of  special  interest  is  the  subcutaneous  inoculation  of  a  pig  with  a 
minimum  quantity  of  mouse's  blood.  From  the  place  of  inoculation  on 
the  right  thigh  a  bluish  discoloration  of  the  skin  spread  over  the  whole 
body  in  spots  and  patches,  while  there  was  considerable  swelling  at  the 
place  of  inoculation.  The  pig  was  dead  in  24  hours.  The  autopsy  re- 
vealed, in  addition  to  the  lesions  mentioned,  exudative  pleuritis  and 
peritonitis,  congestion  of  the  mucous  membrane  of  the  upper  air  pas- 
sages and  of  the  stomach.  A  goat  inoculated  subcutaneously  in  the 
same  manner  was  afflicted  with  extensive  local  inflammatory  oedema  and 
died  within  2  days.  A  horse  inoculated  subcutaneously  in  the  neck 
with  a  suspension  from  an  agar  culture,  derived  originally  from  the 
mouse,  died  within  1£  days  with  extensive  local  reaction,  fluid  blood, 
ecchymoses  on  heart,  pleuritis  and  pericarditis,  and  beginning  inflam- 
mation of  the  mucosa  of  the  stomach. 

The  bacteria  found  by  Kitt  have  a  marked  resemblance  to  swine- 
plague  bacteria,  and  their  pathogenic  eflect  on  pigs  and  smaller  animals 
is  identical  with  that  of  very  virulent  swine-plague  bacteria.  Kitt 
states  that  they  grew  upon  boiled  potato  as  grayish-yellow  colonies, 
whereas  swine-plague  bacteria  do  not  produce  any  visible  growth.  An 

*  Ueber  eine  experimentelle,  der  Rinderseuche  (Bellinger)  ahnliche  Infectionskrank- 
heit.  Sitznngsberichte  der  Gesellschaft  f.  Morphologie  und  Physiologic  in  Miinchen, 
I,  1885,  S.  140-168. 


143 

examination  of  the  text  leads  us,  however,  to  believe  that  he  inoculated 
potatoes  directly  with  blood.  Those  who  have  made  many  cultures 
of  these  bacteria  have  undoubtedly  realized  how  very  richly  cultures 
have  grown  to  which  a  little  blood  was  transferred  from  the  animal 
under  examination.  Hence  the  potato  growths  were  likely  due  to  the 
presence  of  blood.  The  further  statement  that,  after  an  examination  of 
Kitt's  cultures,  Schiitz  considered  these  bacteria  different  from  those  of 
Schweinesenche  (swine  plague)  because  the  latter  did  not  kill  pigeons  is 
worth  nothing,  because  the  difference  is  simply  a  matter  of  virulence.  The 
great  difference  among  swine-plague  bacteria  themselves  as  regards  this 
very  point  we  have  repeatedly  pointed  out. 

A  disease  probably  identical  with  the  foregoing  was  described  by 
Oreste  and  Armaimi,*  as  occurring  among  herds  of  young  buffaloes  in 
Italy.  The  disease  appears  very  suddenly,  and  the  animals  attacked 
may  die  in  from  12  to  24  hours.  The  symptoms  are  high  temperature, 
rapid  and  feeble  pulse,  discharge  of  mucus  from  nose  and  mouth,  asso 
ciated  with  a  local  swelling  on  the  head  and  face  which  leads  to  suffo- 
cation. The  lesions  observed  after  death  are  few  and  inconstant,  a 
hemorrhagic  inflammation  of  the  small  intestine  being  frequently  ob- 
served. The  specific  bacteria  seem  to  be  identical  morphologically  with 
swine-plague  bacteria.  The  disease  can  be  reproduced  in  young  buffa- 
loes by  inoculation  of  cultures.  It  was  similarly  produced  in  a  colt,  a 
cow,  a  sheep,  and  in  mice,  rabbits,  guinea-pigs,  pigeons,  and  fowls. 
Death  ensued  in  all  animals  in  from  1  to  3  days.  Of  two  young  pigs 
inoculated  one  died,  the  other  survived. 

In  France,  Gal  tier  t  has  found  pneu  mo-enteritis  of  swine  associated 
with  a  similiar  disease  in  sheep  which  came  in  contact  with  them. 
While  there  is  much  in  favor  of  his  assumption  that  the  infection  passed 
from  the  swine  to  the  sheep,  the  description  of  the  specific  bacteria  and 
of  the  methods  of  inoculation  are  not  sufficiently  complete  and  thorough 
to  bring  conviction  as  to  the  transmission,  or  furnish  any  definite  in- 
formation concernin  g  the  nature  of  the  bacteria  found.  A  few  sugges- 
tions thrown  out  here  and  there  are  sufficient,  I  think,  to  permit  us  to 
exclude  hog-cholera  bacilli  and  regard  them  as  belonging  to  the  group 
under  consideration. 

These  various  investigations  are  of  great  importance  in  showing  that 
some  infectious  diseases  may  either  attack  several  species  of  domesti- 
cated animals  at  the  same  time,  or  be  inoculable  from  one  species  to 
another.  What  is  of  special  significance  in  the  first  two  investigations 
is  the  extreme  virulence  of  the  bacteria.  The  same  may  be  said  of  the 
Italian  buffalo  disease. 

There  is  another  class  of  infecti  ous  diseases,  due  to  bacteria  of  the 

*  Atti  del  R.  Istituto  d'  incoraggiamento  alle  scienze  natural!,  etc.,  1887.  For  a 
brief  account,  see  also  Journal  de  M6decine  V6t6rinaire,  1887,  p.  585,  and  Baunigar*- 
ten's  Jabresbericht  for  1887,  S.  124. 

t  Journal  de  Me"d.  V6t.,  1889,  passim. 


144 

same  group,  which  produce  specific  diseases  among  certain  species  ot 
domesticated  animals,  but  which  diseases  are  not  known  to  be  com- 
municable to  other  species.  Among  these  are  fowl  cholera,  rabbit  septi- 
caemia, and  a  peculiar  form  of  pleuro-pneumonia  in  cattle,  which  Pools 
has  called  "  septic  pleuro-pneurnonia."  During  the  past  3  or  4  years, 
the  writer  has  examined  in  the  Laboratory  of  the  Bureau  of  Animal  In- 
dustry a  small  number  of  lungs  from  cattle  affected  with  pneumonia 
from  which  bacteria  practically  identical  with  swine-plague  bacteria 
were  isolated.  A  description  and  discussion  of  these  forms  of  pneu- 
monia in  cattle  will  be  reserved  for  a  future  report. 

There  is  thus  a  wide  distribution  of  diseases  among  domesticated 
animals  due  to  a  group  of  bacteria  closely  resembling  and  probably 
identical  with  swine-plague  bacteria.  Some  diseases  attack  several 
species  at  the  same  time ;  others  are,  so  far  as  we  know,  restricted  to  one 
species.  We  have  also  seen  that  there  is  a  wide  distribution  of  attenu- 
ated varieties  among  the  same  domesticated  animals  in  the  healthy 
state,  inhabiting,  so  far  as  our  investigations  have  gone,  the  upper  air 
passages.  Some  observers  are  inclined  to  regard  these  different  bac- 
teria as  practically  the  same.  Hiippe  has  proposed  the  name  septiccvmia 
hcemorrhagica  for  all  the  forms  of  disease  caused  by  them.  Other  ob- 
servers hesitate  to  accept  at  present  this  unifying  explanation.  For 
practical  purposes  the  following  explanation,  based  on  quite  extended 
study  of  this  group  of  bacteria,  may  serve  as  a  provisional  guide  in  the 
prevention  of  disease. 

The  real  test  of  the  power  of  any  bacteria  to  produce  disease  is  viru- 
lence. The  greater  the  virulence  the  more  liable  will  be  the  disease  to 
spread  from  one  species  to  another.  This  is  strikingly  illustrated  by 
the  Wildseuche  of  Bolliuger.  The  relative  virulence  can  be  accurately 
determined  only  by  careful  series  of  inoculations  upon  small  and  large 
experimental  animals,  performed  in  precisely  the  same  way  in  each  case 
with  pure  cultures  of  the  bacteria.  Again,  the  power  of  a  given  disease 
to  pass  from  one  species  to  another  frequently  remains  unnoticed,  partly 
because  the  opportunity  for  such  transmission  is  rarely  given.  Animals 
of  different  species,  such  as  swine,  cattle,  and  sheep,  are  rarely  raised 
and  kept  in  the  same  iuclosures,  because  the  nature  of  food  required 
for  each,  and  other  conditions  lead  to  specialization  in  stock-raising 
and  tend  to  restrict  each  species  to  its  own  pasture  ground. 

It  is  not  unreasonable  to  suppose  that  bacteria  living  in  the  air  pas- 
sages of  one  species,  and  harmless  to  it  to  a  certain  degree,  may  prove  to 
be  disease  germs  with  reference  to  another  species.  Thus  the  attenu- 
ated bajeteria  living  in  the  air  passages  of  healthy  cats,  dogs,  pigs,  and 
cattle,  are  all  fatal  to  rabbits.  In  general,  the  larger  and  more  powerful 
the  animals  the  less  effect  disease  germs  have  upon  them.  It  is  there- 
fore probable  that  some  of  the  outbreaks  of  swine  disease  in  the  West- 
ern States  may  be  due  to  the  cattle  with  which  the  swine  are  herded 
for  feeding  purposes,  The  bacteria  in  cattle,  harmless  to  them,  o^  pec- 


145 

haps  causing  only  mild  disease  and  rarely  observed,  may  prove  the  start- 
ing; point  of  disease  for  swine. 

While  we  have  no  positive  demonstration  of  these  statements,  it  is 
desirable  that  those  engaged  in  stock-raising  should  have  their 'atten- 
tion called  to  the  possibilities  embodied  therein. 

5.  ON  MEASURES  TO  BE  TAKEN  IN  THE  PREVENTION  OF  SWINE  PLAGUE. 

In  regard  to  the  general  measures  to  be  taken  and  the  rules  to  be 
observed  in  the  prevention  of  hog  cholera  and  swine  plague,  we  refer 
the  reader  to  the  report  of  the  Secretary  of  Agriculture  for  1888,  page 
15G,  or  the  report  of  the  Bureau  of  Animal  Industry  for  1887-'S8,  page 
148,  or  the  Special  Report  on  Hog  Cholera,  1889,  page  123.  The  rules 
and  directions  there  formulated  are  adapted  as  well  to  swine  plague,  for 
the  bacteria  of  the  latter  disease  are  even  more  easily  destroyed  by  vari- 
ous agencies  than  are  hog-cholera  bacilli.  In  the  following  pages  only 
the  most  important  points  are  touched  upon. 

The  things  with  which  healthy  swine  should  not  come  in  contact  are, 
in  the  order  of  their  importance,  first  of  all,  diseased  herds  and  ani- 
mals, strange  swine  the  history  of  which  is  not  known,  oft'al  from  estab- 
lishments using  carcasses  of  swine,  recently  infected  ground,  railroads 
carrying  swine,  and  polluted  streams.  Soil  and  water  may  be  infected 
by  living  and  dead  swine  or  any  offal  from  them. 

When  the  disease  has  actually  appeared  in  a  herd  the  question  gen- 
erally arises  whether  it  is  worth  while  to  make  any  attempts  to  save  a 
portion  of  the  herd  or  to  leave  them  to  their  fate.  As  a  rule  it  may  be 
stated  that  it  is  best  to  slaughter  both  healthy  and  diseased  at  once  and 
give  the  surroundings  sufficient  time  to  rid  themselves  of  the  infection 
before  fresh  animals  are  brought  into  them.  If  this  be  not  desirable  we 
should  recommend  the  following  measures  to  be  rigorously  carried  out: 

(a)  Kemoval  of  still  healthy  animals  to  uniufected  grounds  or  pens 
as  quickly  as  possible. 

(b)  Destruction  of  all  diseased  animals. 

(c)  Careful  burial  or  burning  of  carcasses. 

(d)  Repeated  thorough  disinfection  of  the  infected  premises. 

(e)  Great  cleanliness  both  as  to  surroundings  and  as  regards  the 
food. 

If  the  animals  have  been  removed  to  uninfected  grounds,  careful 
watching  is  necessary  to  remove  therefrom  at  once  all  swine  which 
show  signs  of  disease. 

Among  the  various  disinfectants  which  can  be  recommended  are  the 
following: 

1.  Slaked  lime,  in  the  proportion  of  about  5  per  cent  (one-half  pound 
of  lime  to  a  gallon  of  water). 

2.  Equal  volumes  of  crude  carbolic  acid  and  ordinary  sulphuric  acid 
mixed  together  and  added  to  water  in  the  proportion  of  2  ounces  to  a 
gallon  of  water  (1^  volume  per  cent). 

1614 10 


146 

3.  Sulphuric  acid  added  to  water  in  the  proportion   of  1  ounce  to  a 
gallon. 

4.  Boiling  water. 

5.  Corrosive  sublimate  (mercuric  chloride)  in  the  proportion  of  1 
drachm  to  a  gallon  of  water  (1  to  1,000). 

Solution  No.  2  is  said  to  be  more  active  if,  while  the  sulphuric  acid  is 
being  added  to  the  crude  carbolic  acid,  the  vessel  containing  the  latter 
is  placed  in  cold  water  to  prevent  undue  heating  of  the  liquid. 

It  should  be  borne  in  mind  that  sulphuric  acid  and  corrosive  subli- 
mate attack  metals,  and  that  the  solutions  are  best  made  in  wooden 
pails,  etc.  Corrosive  sublimate  is  also  highly  poisonous,  and  the  solu- 
tion should  not  be  made  stronger  than  indicated.  The  lime  is,  on  the 
whole,  the  best  and  cheapest,  but  it  may  not  be  desirable  to  use  it  every- 
where; hence,  one  of  the  others  may  be  substituted.  Each  of  the  solu- 
tions recommended  is  more  than  strong  enough  to  kill  both  hog-cholera 
and  swine-plague  bacteria  and  they  need  not  be  increased  in  strength. 

When  swine  have  become  infected  while  runningover  tracts  of  ground, 
disinfection  of  such  tracts  may  be  regarded  as  practically  impossible. 
If,  however,  thsy  have  been  brought  up  in  pens  or  in  small  inclosures, 
disinfection  should  be  thoroughly  carried  out.  The  woodwork  of  pens 
may  be  disinfected  by  exposing  all  portions,  cracks  and  corners,  to  the 
action  of  any  of  the  solutions  mentioned.  These  may  be  applied  with 
a  broom  or  any  other  household  article  which  insures  uniform  wetting. 
Whitewash  is  useful  for  woodwork  of  fences,  etc.,  when  there  is  no  ob- 
jection to  its  appearance.  Its  action  is  only  exerted  at  the  time  of 
application  and  after  it  has  dried  it  will  not  destroy  bacteria  subse- 
quently adhering  to  it.  It  must,  therefore,  be  applied  fresh  every  time 
disinfection  is  needed.  For  large  farms  some  kind  of  spraying  appa- 
ratus would  be  of  great  service  in  insuring  uniform  distribution  of  the 
disinfectant.  In  the  selection  care  must  be  exercised,  however,  owing  to 
the  corrosive  action  of  some  of  the  solutions.  The  disinfection  of  the 
surface  of  the  soil  over  small  areas  is  perhaps  best  accomplished  by  the 
slaked  lime  or  the  crude  carbolic-acid  solution.  It  should  be  remem- 
bered that  both  preparations  may  be  irritating  to  the  feet  of  animals 
immediately  after  they  have  been  applied.  The  feeding  troughs  should 
receive  special  attention,  and  after  the  application  of  the  disinfectant 
this  should  be  washed  away  with  water,  preferably  hot  or  boiling. 

The  directions  thus  far  given  apply  mainly  to  the  prevention  of  dis- 
ease. When  animals  have  been  actually  attacked,  can  anything  be 
done  for  them  ?  It  has  already  been  stated  that  treatment  of  commu- 
nicable diseases  is  not  a  desirable  thing,  but  even  if  it  were  the  deaths 
follow  each  other  so  rapidly  in  many  outbreaks  that  there  is  no  time 
for  the  application  of  remedies.  If,  however,  an  effort  to  treat  them  is 
to  be  made, ^it  is  desirable  to  avoid  the  various  specifics  and  remedies 
of  unknown  composition,  some  of  which,  thoroughly  tested  at  the  Bureau 
Station  by  Dr.  F.  L.  Kilborne,  were  of  no  ayail  in  checking  the  disease. 


147 

The  sick  animals  should  be  isolated  one  from  another,  as  far  as  possi- 
ble'confined  in  small  inclosures,  kept  quiet,  and  fed  with  moderate 
quantities  of  food,  preferably  with  milk,  if  this  is  to  be  obtained.  If 
the  swine  are  being  fattened  when  the  disease  appears,  this  process 
should  be  stopped  at  once  and  a  light  diet  substituted.  The  tendency 
towards  the  localization  of  disease  in  the  large  intestine,  in  both  swine 
plague  and  hog  cholera,  seems  to  be  due,  at  least  in  part,  to  the  con- 
stipated habits  of  the  pig,  which  permit  the  pathogenic  bacteria  to  re- 
main long  enough  in  the  intestine  to  act  injuriously  upon  the  mucous 
membrane.  Constipation  is  not  easily  overcome,  as  the  trials  with  vari- 
ous cathartics*  have  demonstrated,  and  it  is  highly  important  when 
the  disease  has  appeared  to  feed  a  greater  variety  in  small  quantity  or 
to  follow  the  recommendation  of  giving  the  digestive  organs  a  complete 
rest  by  feeding  milk.  The  boiling  of  food  may  be  desirable,  inasmuch 
as  it  destroys  any  disease-producing  bacteria  which  may  be  present, 
and  makes  digestion  easier.  An  experiment  carried  out  at  the  Bureau 
Station  with  boiled  food  did  not  show  any  more  favorable  results,  how- 
ever, than  with  unboiled  food  ordinarily  given,  so  that  we  can  simply 
suggest  it  for  further  trial. 

Even  if  treatment  should  succeed  after  much  trouble  and  expense  to 
save  some  few  swine,  it  may  not  be  profitable,  owing  to  the  injury  in- 
flicted on  the  various  organs  during  the  disease.  The  lungs  are,  as  a 
rule,  seriously  affected.  They  may  become  adherent  to  the  walls  of  the 
thorax,  and  the  pericardium  may  become  firmly  attached  to  the  heart 
and  impede  its  action.  These  permanent  injuries,  which  no  kind  of 
treatment  yet  suggested  can  avoid,  exercise  an  injurious  influence  on 
the  proper  development  of  the  animal  affected  and  make  its  raising  of 
questionable  advantage.  It  has  already  been  stated  that  such  recov- 
ered animals  may  for  a  time  at  least  be  dangerous  as  carriers  of  the  dis- 
ease germs  to  other  swine. 

The  only  encouraging  line  of  action,  therefore,  lies  in  the  prevention 
of  disease  by  the  observance  of  suitable  precautionary  measures  and 
in  that  general  practice  of  hygienic  laws  which  tfius  tar  has  been  the 
only  means  of  checking  the  rapid  spread  of  epidemics  in  the  human 
family.  The  method  first  suggested  by  Pasteur  of  inoculating  animals 
with  attenuated  cultures,  to  make  them  resist  any  and  every  attack  of 
a  given  infectious  disease,  is,  theoretically  considered,  the  simplest 
means  of  prevention.  Practically,  however,  there  are  two  objections 
which  are  growing  in  importance  year  by  year,  as  our  knowledge  of 
infectious  diseases  is  becoming  broader  and  deeper.  The  method  of 
Pasteur  may  distribute  the  specific  bacteria  far  and  wide  and  become 
a  source  of  future  evil,  since  we  do  not  know  but  that  the  attenuated 
bacteria  may  in  some  way  regain  their  former  virulence.  The  other 
objection  rests  on  the  fact  that  diseases  differ  so  much  one  from  the 
other  that  the  method  seems  to  insure  success  in  only  a  few  diseases. 

*  Special  Report  on  Hog  Cholera,  1889,  p.  135. 


148 

As  regards  swine  plague,  the  experiments  which  have  thus  far 
been  earned  out  indicate  that  this  disease  may  prove  amenable  to  pre- 
ventive inoculation.  We  have  been  able,  by  the  injection  of  both  living 
cultures  and  those  sterilized  at  a  low  temperature  (58°  O.),  to  make 
the  most  susceptible  animals,  rabbits,  insusceptible  to  the  most  virulent 
swine-plague  bacteria.  By  two  subcutaneous  injections  of  cultures  of 
swine-plague  bacteria  swine  have  been  made  insusceptible  to  doses  in- 
jected into  the  circulation,  which  proved  fatal  to  "control"  pigs  within 
24  hours.  In  the  preliminary  experiments  upon  rabbits,  designed  to 
produce  immunity,  several  methods  were  employed.* 

1.  Minute  but  gradually  increasing  quantities  of  culture  liquid  of  very 
attenuated  swine-plague  bacteria  were  injected  at  different  intervals 
into  the  ear  vein  of  rabbits.     Only  a  very  small  proportion  of  these  sur- 
vived the  test  inoculation  with  very  virulent  swine-plague  bacteria. 

2.  Sterilized  bouillon  cultures  were  injected  into  the  abdomen  and 
into  the  circulation  of  rabbits.     This  method  also  produced  immunity 
and  partial  resistance,  but  in  only  a  comparatively  few  animals. 

3.  The  preceding  method  was  modified  in   the  following  manner : 
Swine-plague  bacteria  from  outbreak  IX  were  allowed  to  produce  for 
2  days  a  rich  growth  upon  agar.     This  growth  was  scraped  off  and  a 
very  turbid  suspension  in  bouillon  prepared  and  sterilized  at  58°  C. 
With  this  sterilized  suspension  injections  were  made  into  the  abdomen 
of  rabbits  as  follows : 


Rabbit  No. 

May  4. 

May  8. 

May  14. 

May  22. 

Total. 

Remarks. 

cc. 

cc. 

cc. 

cc. 

cc. 

f 

Nos.  35,  30,  and  37  inoculated  with 

35      

1.  5 

1 

2 

3 

7  5  1 

36          .     . 

2 

.  5 

2 

3 

7  5< 

Check  dies  over  ni<rht.    All  three 

37  

1 

1.5 

2 

3 

75] 

survive  with  considerable  local  re- 

1 

action. 

38  

.5 

2 

2 

4.5 

Inoculated  with  virulentswine  plague 

May  19,  dies  in  6  days  with  severe 

local  reaction,  plenritis,  and   peri- 

carditis.   The  check  dies  in  16  to  20 

hours. 

These  results  show  very  decisively  the  protective  effect  of  the  steril- 
ized growth  of  swine-plague  bacteria.  Additional  experiments  have 
not  yet  been  made. 

In  conjunction  with  Dr.  Kilborne,  the  protective  effect  of  swine-plague 
cultures  was  tested  upon  swine  in  the  following  experiment :  Seven  pigs 
belonging  to  the  same  lot  and  about  4  months  old  were  chosen,  three 
of  which  were  set  aside  as  "  control"  animals  or  checks.  The  remain- 
ing four  received  February  28,  1891,  a  subcutaneous  injection  of  G  cubic 
centimetres  of  peptone-bouillon  culture  of  virulent  swine-plague  bac- 
teria (outbreak  IX),  one-half  into  each  thigh.  As  a  result  one  died.t 
The  remaining  three  were  reinoculated  in  the  same  way  March  14, 

*  These  experiments  were  carried  out  in  conjunction  with  Dr.  V.  A.  Moore. 
t  See  p.  74  for  autopsy  notes. 


149 


receiving  on  this  date  10  cubic  centimetres  of  culture  liquid.  April  3, 
these,  together  with  the  three  control  animals  or  checks,  received  the 
linal  test  inoculation;  li  cubic  centimetres  of  peptone-bouillon  culture  of 
the  same  bacteria  were  injected  into  a  vein  of  the  leg  of  each  animal. 
Two  of  the  control  animals  died  within  24  hours,  the  third  in  36  hours. 
None  of  the  three  vaccinated  animals  became  ill.  No  symptoms  of  dis- 
ease or  lesions  appeared  subsequently. 

These  experiments  simply  demonstrate  the  fact  that  swine  may  be 
protected  from  fatal  doses  by  subcutaneous  injection.  Whether  this 
process  would  be  successful  in  natural  outbreaks  can  not  be  inferred 
from  this  test.  The  method  is  open  to  the  objection  above  mentioned, 
i.  e.,  it  is  liable  to  distribute  the  specific  bacteria  wherever  vaccination 
is  practiced.  Since  the  more  desirable  one  of  injecting  the  products  of 
bacterial  growth  is  now  being  tested  there  is  no  need  of  any  further 
discussion  of  this  subject  at  the  present  time. 

CONCLUSIONS. 

1.  There  are  two  independent  infectious   diseases  of  swine — swine 
plague  and  hog  cholera — each  caused  by  an  easily  recognizable,  specific 
disease  germ. 

2.  Swine  plague  (in  those  outbreaks  which  have  come  to  our  notice) 
is  limited  chiefly  to  the  lungs  in  its  destructive  effect..  The  intestines 
may  be  and  frequently  are  involved  in  the  disease  process.     Hence  it  is 
an  infectious  pneumo-enteritis  rather  than  an  infectious  pneumonia.  * 

3.  There  is  considerable  variation  in  the  virulence  or  disease-produc- 
ing power  of  swine-plague  bacteria  from   different  outbreaks.    The 
greater  the  virulence,  other  things  being  equal,  the  severer  and  more 
extensive  the  epizootic. 

4.  The  bacteria  of  iSchiceineseucJie  (German  disease  of  swine)  are  iden- 
tical with  those  of  swine  plague. 

5.  In  the  upper  air  passages  of  a  certain  percentage  of  healthy  swine, 
cattle,  dogs,  and  cats,  bacteria  exist  which  belong  to  the  species  of 
swine-plague  bacteria,  and  which  as  a  rule  possess  a  relatively  feeble 
virulence.     While  it  is  probable  that  such  bacteria  may  produce  disease 
it  may  be  regarded  as  pretty  certain  that  it  is  largely  aided  by  second- 
ary causes  producing  unthriftiness,  and  is  merely  sporadic  and  not 
communicable. 

G.  In  many  epizootics  of  swine  disease  both  hog-cholera  and  swine- 
plague  bacteria  as  well  as  the  respective  lesions  of  these  bacteria  co- 
exist. Such  mixed  diseases  are  due  to  the  frequent  presence  of  both 
bacteria  in  the  surroundings  of  swine,  probably  a  result  of  frequent  in- 
troduction. Either  disease  may  be  primary  according  to  its  relative 
virulence. 

7.  It  is  highly  probable  that  the  many  attenuated  varieties  of  either 
disease  germ  can  produce  disease  only  when  assisted  by  the  other  germ 


150 

or  by  the  unsanitary,  unphysiological  methods  of  rearing  swine  by  which 
the  latter  are  reduced  in  vitality  and  made  more  susceptible. 

8.  It  is  pretty  well  established  that  there  are  a  number  of  infectious 
diseases  affecting  cattle,  buffaloes,  deer,  fowls,  and  smaller  animals, 
the  bacteria  of  which  are  closely  related,  if  not  identical  with,  those  of 
swine  plague.    These  plagues  appear  in  various  parts  of  the  globe  spo- 
radically.    ( Wild-  und  Rinderseuclie,  barbone  bufalino,  fowl  cholera,  rab- 
bit septicajtnia.)    Their  tendency  to  spread  from  one  species  to  another, 
from  cattle  to  swine,  for  instance,  probably  depends  both  on  the  degree 
of  virulence  of  the  bacteria  as  well  as  the  opportunities  afforded  for 
such  transmission. 

9.  Swine-plague  bacteria  are  very  probably  introduced  into  a  herd 
only  in  the  bodies  of  animals,  since  they  are  speedily  destroyed  in  soil 
and  water  by  natural  agencies.    Virulent  varieties  are  perhaps  always 
derived  from  preexisting  disease.    Attenuated  varieties  may  be  intro- 
duced by  healthy  animals.     Since  these  may  under  special  conditions 
give  rise  to  disease,  efforts  to  prevent  and  suppress  infection  must  take 
into  account  the  physical  condition  of  the  exposed  animals. 


APPENDIX. 


THE  PRESENCE  OF  SEPTIC  BACTERIA,  PROBABLY  IDENTICAL  WITH  THOSE  OF  SWINE 

PLAGUE,  IN  THE  UPPER  AIR  PASSAGES  OF  DOMESTICATED  ANIMALS 

OTHER  THAN  SWINE. 


By  VERANUS  A.  MOORE,  B.  S.,  M.  D.,  Assistant. 


The  examination  of  the  secretions  of  the  mucous  membrane  of  the 
upper  air  passages  in  domesticated  animals  other  than  swine  was  be- 
gun under  the  direction  of  Dr.  Theobald  Smith  for  the  purpose  of  deter- 
mining whether  or  not  the  swine-plague  germ,  or  a  germ  closely  related 
to  it,  is  normally  present  in  these  animals.  The  results  obtained  from 
the  limited  number  of  examinations  that  have  been  made  from  the 
various  animals  are  of  so  much  value  in  throwing  light  upon  the  natural 
habitat  of  this  group  of  microorganisms  that  a  preliminary  report  of 
these  experiments  seemed  desirable  at  this  time. 

The  methods  that  have  been  employed  in  these  investigations  are  the 
same  as  those  used  by  Dr.  Smith  in  the  examination  of  mucus  from 
the  respiratory  tract  of  healthy  pigs,  and  which  are  described  on  p. 
110  of  this  report.  The  inoculations  of  rabbits  with  the  mucus  from 
the  various  animals  were  made  in  part  conjointly  with  Dr.  F.  L.  Kil- 
borue,  in  part  by  him  alone,  and  in  a  few  cases  I  alone  am  responsible 
for  these  operations. 

1.  Inoculations  from  cattle. — Rabbits  have  been  inoculated  with  the 
mucus  taken  from  the  larynxoramygdaloid  cavities  of  seven  healthy  cat- 
tle. Four  of  these  were  steers,  two  of  which  were  Western  animals  that 
had  been  shipped  to  Washington  for  beef.  The  four  steers  were  killed 
in  a  slaughter-house  near  the  Experiment  Station  by  cutting  the  blood 
vessels  in  the  neck.  Care  was  taken  to  keep  the  mouth  free  from  blood. 
The  other  three  were  heifers  that  were  killed  for  various  purposes  in  a 
similar  manner  at  the  Experiment  Station.  In  each  case  the  mucus  was 
collected  immediately  after  the  death  of  the  animal  and  inoculated  sub- 
cutaueously  into  rabbits. 

The  rabbits  that  were  inoculated  with  the  mucus  from  the  four  steers 
and  one  of  the  heifers  died  in  from  3  to  G  days.  The  lesions  found  in 
these  rabbits  were  similar  to  those  produced  by  the  attenuated  swine- 

151 


152 


plague  gerin.  The  local  infiltration  contained  several  forms  of  bacteria. 
In  the  peritoneal  exudate  and  in  the  spleen  and  liver  bacteria  were 
found  that  resembled  the  swine-plague  germ  both  in  stained  cover-glass 
preparations  from  the  tissues  and  in  cultures. 

The  rabbits  inoculated  from  the  two  remaining  animals  showed  no 
signs  of  disease. 

The  pathogenic  effect  of  the  bacteria  obtained  from  the  first  two  cat- 
tle was  determined  by  inoculating  rabbits  with  pure  cultures.  The 
subcutaneous  injection  produced  extensive  purulent  infiltration  at  the 
point  of  inoculation  and  exudative  peritonitis,  destroying  the  rabbit  in 
G  days.  An  intravenous  inoculation  of  the  same  quantity  of  a  similar 
culture  from  the  second  case  proved  fatal  in  24  hours.  The  blood,  liver, 
and  spleen  contained  innumerable  bacteria  which  could  not  be  distin- 
guished from  the  swine-plague  germ.  No  inoculations  were  made  with 
pure  cultures  from  the  remaining  three  animals.  It  is  sufficient  to  say 
that  the  lesions  produced  in  all  of  the  rabbits  inoculated  from  the  five 
cases  were  the  same.  The  following  tables  will  explain  the  results  of 
these  inoculations : 

Inoculation  of  rabbits  with  mucus  from  the  upper  air  passages  of  cattle. 


Aiii- 
No. 

Mucus 
from— 

Rabbit 
inocu- 
lated, 
No. 

Date  of 
inocula- 
tion. 

Rabbit 
died 
in— 

Remarks. 

1890. 

Days. 

1 

Amygda- 

(        1 

Feb.  27 

3 

Local  reaction  ;  peritonitis. 

loid  cav- 

/ 

ities. 

I         2 

Feb.   27 

4 

Do. 

2 

Feb.  27 

4 

Local  reaction;  peritonitis;  pleuritis. 

Larynx  ... 

)         4 

Feb.  27 

4 

Local  reaction  ;  peritonitis  ;  pleuritis  and  pericar- 

£ 

ditis. 

3 

Amygda- 

5 

Mar.  13 

3 

Local  reaction  ;  peritonitis. 

loid  cav- 

ities. 

4 

...  do  

6 

Apr.    1 

4 

Local  reaction;   peritonitis;  beginning  plenritis. 

5 

...  do  

7 

Mar.  20 



Rabbit  remained  well. 

G 

Larynx  .  .  . 

C         8 

Oct.     2 
Oct.      2 

4 
6 

Local  reaction  ;  peritonitis. 
Do. 

1891. 

7 

Amygda- 

C      10 

Jan.     5 

Rabbit  remained  well. 

loid  cav- 

5 

ities. 

/  11 

Jan.     5 

Do. 

Inoculations  with  pure  cultures  obtained  from  above  rabbits. 


Culture 

| 

Rabbit 

rabbit 

Method  of  inoculation  and  date. 

died 

Remarks. 

No. 

in  — 

- 

Days. 

1 

Marcb  4,  1890,one-eightb  cubic  centimetre  bouillon*  culture 
snbcutaneously. 

G 

Local  reaction  ; 
peritonitis. 

3 

March  4,  1890,  one-eighth  cubic  centimetre  bouillon  culture 

1 

Septicasmia. 

into  ear  vein. 

1 

*  All  the  bouillon  used  in  these  investigations  contained  one-fourth  per  cent,  of  peptone. 

2.  Inoculations  from  cats. — Eabbits  were  inoculated  with  the  secre- 
tions of  the  mucous  membrane  of  trachea,  larynx,  or  pharynx  of  seven 


153 


healthy  cats.  The  cats  were  raised  in  and  about  Washington,  but  not 
on  the  Experiment  Station.  They  were  killed  either  by  a  shot  through 
the  heart  or  with  chloroform,  and  the  mucus  was  removed  with  every 
precaution  immediately  after  death. 

The  rabbits  that  were  inoculated  from  cat  No.  6  remained  well.  All 
of  the  others  died.  The  result  of  these  inoculations  is  of  particular  in- 
terest, as  the  rabbits  died  in  from  1  to  7  days,  and  presented  lesions  sim- 
ilar to  those  produced  by  the  swine-plague  germ  in  its  most  virulent  as 
well  as  its  attenuated  forms.  From  the  various  organs  of  all  the  rab- 
bits bacteria  were  found  which  could  not  be  distinguished  from  each 
other  or  from  the  swine-plague  germ. 

The  virulence  of  pure  cultures  obtained  from  the  rabbits  inoculated 
from  cats  I,  2,  and  3  was  tested  by  both  intravenous  and  subcutaneous 
inoculations  on  fresh  rabbits.  These  proved  fatal  in  from  18  to  48 
hours.  The  blood  and  other  organs  contained  innumerable  bacteria. 
The  cultural  characters  of  these  germs  will  be  mentioned  in  another 
place.  The  accompanying  tables  give  a  summary  of  these  inoculations: 

Inoculation  of  rabbits  with  mucltn  from  the  upper  air  passages  of  cats. 


Cat 
No. 

How  killed. 

Mucus 
from  — 

Rabbit 
inocula- 
ted, No. 

Date  of 
inocula- 
tion. 

Rabbit 
died  in  — 

Remarks. 

1890. 

Dayg. 

1 

Shot  through 
heart. 

£  Larynx  .. 

C          12 
i           13 

Apr.  22 
Apr.  22 

13 

7 

Local  reaction  ;  peritonitis 
Local  reaction  ;  peritonitis,  pleuri- 

tis,  pericarditis. 

2 

....do  

....do  .... 

<           14 
i           15 

Apr.  22 
Apr.  22 

2 
3 

Local  reaction  ;  peritonitis. 
Do. 

3 

...do  

Pharynx. 

16 

June  11 

1 

Septicaemia. 

4 

....do  

....do  .... 

17 

June  11 

1 

Do. 

5 

....do  

Larynx  .. 

18 

Dec.   26 

i* 

Slight  local  reaction,  beginning  per- 

itonitis. 

1891. 

C           19 

Jan.     6 

Rabbit  remained  well. 

6 

Chloroformed 

Trachea  . 

)           20 

Jan.     6 

Do. 

7 

....do  

....do.... 

<           21 
\           22 

Jan.   24 
Jan.  24 

3 
5 

Local  reaction;  beginning  pleuritis. 
Local  reaction;  pleuritis. 

Inoculations  with  pure  cultures  obtained  from  above  rabbits. 


Culture 
from  nib- 
bit  No. 

Method  of  iuoculation  and  date. 

'Rabbit 
died  in— 

Remarks. 

Hours. 

12J 

A  nr.2i),  1890,  one-eighth  cubic  centimetre  bouil- 
lon culture  into  ear  vein. 

20 

Septicaemia. 

12 

May  2,  ISsN),  loop  agar  culture  subciitaneously 

60 

Beginning  peritonitis. 

I 

in  ear. 

14 

May  10,1890,one-eighlh  cubic  centimetre  bouil- 

18 

Septicaemia. 

lon  culture  into  ear  vein. 

15 

May  10,  1890,  one  eighth  cubic  centimetre  bouil- 

36 

Slight  local  reaction  ;  sep- 

lon culture  subcutaneously. 

ticaemia. 

1C 

...do  

18 

Septicaemia. 

3.  Inoculations  from  dogs. — Rabbits  were  inoculated  with  the  mucus 
taken  from  the  larynx  or  upper  pharynx  of  six  healthy  dogs.  These 
were  also  procured  in  Washington  City  and  its  suburbs.  They  were 
killed  by  a  shot  through  the  heart.  The  mucus  was  removed  imme- 
diately after  death  and  at  once  inoculated. 


154 


The  rabbits  inoculated  from  dogs  IsTos.  2  and  3  died  in  about  36  hours. 
Innumerable  bacteria  were  found  in  the  various  organs  that  could  not 
be  distinguished  from  those  obtained  from  cattle  and  cats  or  from  the 
swine-plague  germ.  The  rabbits  inoculated  from  the  other  four  dogs  re- 
mained well.  Both  subcutaneous  and  intravenous  inoculations  of  fresh 
rabbits  with  cultures  of  these  bacteria  proved  that  they  were  as  viru- 
lent as  those  from  several  of  the  cats.  The  results  of  these  inoculations 
are  summarized  in  the  appended  tables : 

Inoculation  of  rabbits  mith  mucus  from  the  upper  air  passages  of  dogs. 


Dog 
NoT 

Mucus 
from  — 

Eabbit 
inocula- 
ted. No. 

Date  of 
inocula- 
tion. 

Eabbit 
died 
in  — 

Remark  a. 

V          23 

1890. 
Apr.  29 

Hours. 

Rabbit  remained  welL 

1 

Larynx  .  .  . 

1          24 

Apr.  25 

Do. 

2 
3 

4 

Pharynx.. 
Larynx  ..* 
do  

25 
26 
21 

Apr.  28 
May     9 
May  26 

30 
36 

Local  reaction,  beginning  pleuritis. 
Local  reaction,  peril  onitis. 
Kabbit  remained  welL 

5 

..  do  

28 

May  31 

Do 

6 

....do  

29 

Dec.     6 

Do. 

Inoculations  with  pure  cultures  obtained  from  above  rabbits. 


Culture 

Rabbit 

from 

Method  of  inoculation  and  date. 

died 

Remarks. 

rabbit 

No.— 

in  — 

Hours. 

25 

May  2,  1890,  loop  agar  culture  subcutaneotisly  in 

22 

Septicaemia. 

ear. 

f 

May  20,  1890,  one-eighth  cubic  centimetre  bouillon 

18 

Do. 

1 

culture  into  oar  vein. 

26  •> 

May  20,  1890,  one-eighth  cubic  centimetre  bouillon 

18 

Do. 

( 

culture  subcutanooiisly. 

4.  Inoculations  from  other  animals. — Eabbits  have  been  inoculated 
with  the  mucus  taken  from  the  larynx  or  trachea  of  one  sheep,  one 
horse,  two  old  fowls,  and  one  rabbit.  One  of  the  two  rabbits  inocu- 
lated from  the  sheep  developed  a  large  abscess  near  the  point  of  inocu- 
lation. It  was  chloroformed  after  about  one  month.  There  were  no 
other  lesions.  The  other  rabbits  remained  well.  The  inoculations  from 
a  single  animal  are,  of  course,  insufficient  to  give  any  general  informa- 
tion respecting  the  species.  The  annexed  table  gives  all  the  informa- 
tion necessary  with  reference  to  these  inoculations. 

Inoculations  icith  mucus. 


Animal. 

How  killed. 

Mucus 
from  — 

Rabbit 
inocula- 
ted. No. 

Date  of 
inocula- 
tion. 

Remarks. 

1890. 

Sheep  1  ... 

Cutting  jugulars.. 

Larynx  .  .  . 

C          30 
)           31 

Apr.     7 
Apr.     7 

Local  abscess;  chloroformed. 
Rabbit  remained  well. 

Horse  1... 

Shot  

....do  .  ... 

C           32 
)           33 

Apr.     7 
June    3 

Do. 
Do. 

Fowl  1.   . 

Trachea  .. 

34 

June    3 

Do. 

Fowl  2  

...  no     

....do  

35 

Do. 

1891. 

Rabbit  1  .  . 

Chloroformed  

....do  

36 

Apr. 

Do. 

155 

It  will  be  seen  from  the  experiments  given  that  a  germ  which  is  not 
distinguishable  from  the  swine-plague  germ  was  found  in  the  mucus 
from  the  upper  air  passages  of  71  per  cent,  of  the  cattle,  85  per 
cent,  of  the  cats,  and  33  per  cent  of  the  dogs  from  which  inocula- 
tions were  made.  When  the  rabbit  lived  for  more  than  24  hours 
after  its  inoculation  there  was  a  purulent  infiltration  of  the  skin  and 
subcutis  at  the  point  of  inoculation.  The  infiltration  extended  over  an 
area  varying  in  size  in  proportion  to  the  length  of  time  which  the  animal 
lived.  In  some  cases  it  covered  the  entire  ventral  aspect  of  the  body. 
Occasionally  there  was  in  addition  a  sanguinolent  effusion  which  ex- 
tended beyond  the  limits  of  the  infiltration.  The  local  reaction  was 
undoubtedly  increased  by  the  presence  of  other  bacteria  that  were  in- 
troduced with  the  mucus.  The  internal  lesions  were  characterized  by 
an  inflammatory  condition  produced  by  the  localization  of  the  germs 
on  some  one  or  more  of  the  serous  membranes,  notably  the  peritoneum, 
when  the  rabbit  did  not  die  from  a  rapidly  fatal  septicaemia. 

It  is  interesting  to  note  that  the  inoculations  made  from  cattle  proved 
fatal  in  from  3  to  6  days,  and  that  the  resulting  lesions  in  every  instance 
were  characteristic  of  attenuated  swine  plague.  In  the  rabbit  that 
lived  6  days  there  was  severe  peritonitis,  while  in  three  that  lived  only 
4  days  there  were  both  peritonitis  and  pleuritis  and  in  one  case  peri- 
carditis. The  rabbit  which  lived  6  days  after  inoculation  with  a  pure 
culture  exhibited  in  addition  to  the  local  reaction  only  peritouitis. 

In  the  inoculations  from  cats  we  find  a  much  wider  range  in  the  char- 
acter of  the  lesions  produced.  The  rabbits  inoculated  from  cats  Nos.  3 
and  4  were  victims  of  a  rapidly  fatal  septicaemia,  the  swine-plague  bac- 
teria being  distributed  in  enormous  numbers  throughout  the  blood  and 
internal  organs.  The  rabbit  inoculated  from  cat  No.  5  lived  about  12 
hours  longer  and  exhibited  beginning  peritonitis.  The  localization  of 
these  germs  on  the  peritoneum  is  further  illustrated  in  rabbits  Nos.  12, 
14,  and  15.  These  animals  lived  2  and  3  days  and  died  with  exudative 
peritonitis.  In  the  exudate  there  were  innumerable  bacteria,  but  com- 
paratively few  were  found  in  the  blood.  In  rabbit  13  we  have  a  marked 
example  of  the  distribution  of  these  germs  over  the  entire  serous  sur- 
faces of  the  trunk.  Both  rabbits  from  cat  No.  7  are  interesting,  as  the 
lesions  were  confined  to  the  pleura.  In  these  cases  the  pleuritic  exu- 
date contained  innumerable  swine-plague  bacteria  while  the  blood  con- 
tained only  a  few.  This  emphasizes  the  fact  that  in  cases  of  well- 
marked  localization  there  are  comparatively  few  germs  in  the  general 
circulation  at  the  time  of  death. 

The  rabbits  that  were  inoculated  from  dogs  Nos.  2  and  3  lived  the 
same  length  of  time  as  the  rabbit  inoculated  from  cat  No.  5.  It  is  in- 
teresting to  note  that  the  rabbit  inoculated  from  No.  2  exhibited  pleu- 
ritis and  the  one  from  dog  No.  3  peritonitis.  Here  again  we  have  a 
marked  illustration  of  the  variable  localization  of  this  group  of  micro- 
organisms when  their  virulence  is  not  sufficient  to  destroy  the  rabbit 


166 

in  from  18  to  24  hours.  The  tendency  to  localization  is  well  shown  in 
the  following  summary  of  the  lesions  found  in  the  nineteen  rabbits  that 
have  succumbed  to  the  inoculations  from  the  different  animals: 


Lesions. 

No.  of 

rabbits. 

Per  cent. 

Local  reaction,  peritonitis  

10 

52.6 

3 

15.7 

Local  reaction,  peritonitis,  and  pleuritis  

2 

10.5 

Local  reaction,  peritonitis,  pleuritis,  and  pericarditis  

2 

10.5 

Septicaemia  

2 

10.5 

The  inoculations  with  pure  cultures  of  the  bacteria  obtained  from 
the  different  rabbits,  although  few  in  number,  are  important,  as  they 
verify  the  results  obtained  from  the  original  inoculations.  The  sub- 
cutaneous inoculation  with  one-eighth  cubic  centimeter  ot  a  bouillon 
culture  of  the  germ  from  cattle  resulted  in  extensive  local  reaction 
and  peritonitis.  The  inoculation  of  a  rabbit  subcutaneously  in  the 
ear  with  a  loop  of  an  agar  culture  from  cat  No.  1  is  also  interesting, 
as  it  not  only  lived  nearly  as  long  as  the  original  rabbit,  but  devel- 
oped peritonitis.  The  rabbit  inoculated  subcutaneously  with  a  culture 
from  cat  No.  2  is  the  only  rabbit  in  these  experiments  that  lived  over 
24  hours  without  exhibiting  some  point  of  localization  of  the  germs  on 
the  serous  membranes. 

The  difference  in  the  virulence  of  the  germs  obtained  from  cattle,  cats, 
and  dogs,  and  the  consequent  variations  in  the  character  of  the  lesions 
produced  in  rabbits,  are  paralleled  in  similar  inoculations  from  pigs  and 
with  cultures  of  the  swine-plague  bacteria  obtained  from  sporadic  cases 
and  the  different  outbreaks  of  that  disease,  I  have,  therefore,  not 
found  in  the  inoculations  of  rabbits  any  pathogenic  property  possessed 
by  any  of  the  septic  germs  discovered  in  the  upper  air  passages  of 
healthy  animals  that  will  differentiate  them  from  the  swine-plague  bac- 
teria. 

Cultural  characters. — From  the  blood  or  spleen  of  each  rabbit  cultures 
were  made  on  agar  or  in  bouillon.  From  these,  subcultures  were  made 
in  the  various  culture  media  employed  in  differentiating  bacteria  for 
the  purpose  of  determining,  if  possible,  any  cultural  differences  that 
might  exist  between  them,  or  between  them  and  the  swine-plague  bac- 
teria. As  these  cultures  were  obtained  at  different  times  and  the  media 
used  prepared  on  different  dates  the  occasional  slight  variations  in  the 
character  of  the  growth  that  were  observed  between  the  different  bac- 
teria could  not  be  considered  as  constant  differences,  as  it  was  found 
that  these  bacteria,  like  those  of  swine  plague,  do  vary  slightly  in  cul- 
ture media.  In  view  of  this  fact  two  series  of  comparative  cultures 
have  been  made  on  the  different  media,  each  medium  being  prepared 
from  the  same  material  and  at  the  same  time. 

The  comparative  cultures  were  made  (1)  from  cultures  of  bacteria  ob- 


157 

tained  from  a  healthy  pig,  cat,  and  dog ;  (2)  from  cultures  of  attenuated 
and  of  virulent  swine-plague  bacteria,  and  (3)  from  cultures  of  swine 
plague  bacteria  found  in  a  guinea-pig  that  died  of  sporadic  pneumonia. 
Unfortunately  the  germs  from  the  upper  air  passages  of  cattle  had 
perished  at  the  time  the  comparative  cultures  were  made. 

(«)  Nutrient  agar. — The  growths  of  the  various  bacteria  upon  this  substratum  were 
not  distinguishable  one  from  the  other. 

(6)  Alkaline peptonized  bouillon. — The  growth  in  the  bouillon  cultures  made  from 
the  blood  or  spleen  of  a  few  of  the  rabbits  consisted  of  small,  grayish  flukes.  These 
were  at  first  held  in  suspension  in  the  liquid,  but  soon  settled,  leaving  the  supernatant 
culture  fluid,  perfectly  clear.  This  character  was  not  constant,  as  the  clumps  of 
growth  gave  way  to  a  uniform  cloudiness  of  the  culture  liquid  after  a  short  scries  of 
subcultures.  The  bouillon  cultures  from  all  of  the  other  rabbits  were  uniformly 
clouded. 

In  the  first  series  two  of  the  germs  grew  in  clumps.  The  others  imparted  a  uniform 
cloudiness  to  the  liquid.  After  7  days  standing  the  growth  had  settled  in  the  bottom 
of  the  tube  in  the  two  cultures  that  contained  clumps.  In  the  others  a  thin,  grayish, 
somewhat  viscid  band  composed  of  bacteria  was  formed  on  the  sides  of  the  tube  at 
the  surface  of  the  liquid.  The  latter  was  faintly  clouded.  The  growth  of  the  viru- 
lent swine-plague  gerin  seemed  less  vigorous  than  that  of  the  others.  In  about  3 
weeks  there  was  a  considerable  quantity  of  a  grayish,  viscid  sediment  in  the  bottom  of 
the  tubes  which  upon  agitation  was  forced  up,  appearing  as  a  somewhat  twisted,  tena- 
cious cone  with  its  apex  at  the  surface  of  the  liquid. 

In  the  second  series  the  growth  in  all  of  the  cultures  imparted  a  uniform  cloudiness 
to  the  liquid.  In  4b  hours  the  virulent  swine-plague  culture  was  nearly  cleared.  In 
7  days  the  cultures  of  the  bacteria  from  the  healthy  pig  and  cat  and  from  the  guinea- 
pig's  lung  were  clear.  The  cultures  of  the  attenuated  swine-plague  germ  and  the 
germ  from  the  healthy  dog  remained  clouded.  In  every  case  the  grayish  band  formed 
on  the  sides  of  the  tube  at  the  surface  of  the  liquid  as  in  four  of  the  cultures  in  the 
first  series.  The  sediment  in  the  bottom  of  the  tubes  was  small  in  quantity  and  fria- 
ble. The  reaction  of  all  of  the  cultures  was  decidedly  acid  after  24  hours  ;  less 
strongly  so  after  4  weeks.  The  difference  in  the  character  of  the  sediment  in  the  two 
series  of  cultures  was  very  marked.  This  same  variation  has  been  observed  in  other 
bouillon  cultures  of  the  same  bacteria.  It  is  important  to  add  that  the  variation  in 
the  character  of  the  growth  in  bouillon  cultures  of  any  one  of  these  germs  has  been 
found  to  be  as  great  as  that  between  cultures  of  the  bacteria  from  different  sources. 

Although  these  bacteria  change  the  reaction  of  an  alkaline  bouillon  to  an  acid 
one  during  their  multiplication,  they  will  not  grow  when  inoculated  into  peptonized. 
beef-broth  that  has  not  been  neutralized. 

(c)  Peptonized  bouillon  containing  2  per  cent,  glucose. — The  growth  of  the  various 
bacteria  in  fermentation  tubes  containing  this  liquid  does  not  vary  in  the  cultures 
examined. 

(d)  Gelatine. — The  growth  in  this  medium  is  uncertain.     The  germ  from  cat  No.  2 
developed  minute  grayish  colonies  in  roll  cultures.    They  were,  however,  too  small 
for  diagnostic  purposes.     One  of  the  swine-plague  germs  occasionally  developed  mi- 
nute colonies.     The  other  bacteria  did  not  grow,  although  a  largo  number  of  cultures 
were  made  from  each. 

(e)  Potatoes. — No  growth. 

(/)  Milk. — No  appreciable  change  in  the  appearance  of  the  milk  was  produced. 
Slightly  acid  in  reaction.  Cover-glass  preparations  showed  a  vigorous  multiplication 
of  the  bacteria  in  every  culture.  In  this  medium  the  bacteria  appeared  as  rods 
longer  than  under  other  conditions  under  which  they  have  been  examined. 

From  both  the  comparative  cultures  and  the  large  number  of  cul- 
tures that  have  been  made  at  other  times,  I  have  thus  far  been  unable 


158 

to  detect  any  cultural  character  that  is  sufficiently  constant  to  differ- 
entiate the  bacteria  in  question,  the  one  from  the  other. 

PNEUMONIA  AND   PLEURITIS  IN   A   GUINEA-PIG  CAUSED  BY  BACTERIA 
CLOSELY  RESEMBLING  THOSE  OF  SWINE  PLAGUE. 

On  December  24,  1890,  a  large  adult  female  guinea-pig  was  found 
dead  in  a  pen  where  several  of  the  supply  animals  were  kept.  A  care- 
ful examination  of  this  animal  revealed  the  following  conditions : 

Beneath  the  skin  near  the  left  mamma  a  closed  abscess.  Swelling  and  ulceratiou  of 
the  left  fore  foot.  Spleen  normal.  Liver  fatty.  No  intestinal  lesions.  In  the  pleural 
cavity  a  considerable  quantity  of  a  grayish,  viscid  exudate  lining  the  costal  and 
pulmonary  pleura.  The  anterior  half  of  both  lungs  hepatized.  Suppurative  peri- 
carditis. Cover-glass  preparations  from  the  pleura!  exudate  contained  a  very  largo 
number  of  bacteria  not  distinguishable  from  swine-plague  bacteria.  In  an  agar  tube 
inoculated  with  the  exudate  a  pure  culture  of  these  bacteria  developed. 

A  rabbit  inoculated  subcutaneously  with  a  very  small  quantity  of  the  pleural  exu- 
date died  in  less  than  20  hours.  Innumerable  swine-plague  bacteria  were  found 
in  the  liver,  blood,  and  spleen.  The  polar  stain  so  characteristic  of  the  swine-plague 
germ  was  well  marked  in  the  cover-glass  preparations  from  all  of  the  tissues.  A  pure 
culture  of  this  germ  was  obtained  from  the  blood. 

In  order  to  test  still  further  the  virulence  of  this  germ,  a  second  rabbit  was  inocu- 
lated subcutaueously  with  an  equivalent  of  one-five  hundredth  cubic  centimetre  of  a 
bouillon  culture  made  from  the  blood  of  the  first  rabbit.  This  inoculation  proved 
fatal  in  about  24  hours.  Innumerable  swine-plague  bacteria  were  found  in  the 
various  organs. 

The  cultures  of  this  germ  on  the  various  media  could  not  be  distin- 
guished from  those  of  the  virulent  swine-plague  germ. 

Dr.  Kilborne  informs  us  that  prior  to  the  death  of  this  guinea-pig,  of 
which  a  bacteriological  examination  was  made,  others  had  been  found 
dead  from  time  to  time  at  the  Experiment  Station  without  exposure  to 
any  disease.  A  cursory  examination  had  shown  that  a  considerable 
number  of  these  had  died  from  exudative  pleuritis  with  or  without 
pneumonia. 

DISEASE  IN   A  FOWL  ASSOCIATED   WITH    BACTERIA  CLOSELY  RESEM- 
BLING  THE  FOREGOING. 

On  April  25L,  1891,  two  large,  well-nourished  hens  were  found  dead  in 
a  flock  of  fowls  that  are  kept  on  the  Experiment  Station.  A  few  days 
prior  to  this  a  fowl  had  died,  but  it  was  not  examined.  There  had 
been  no  evidence  of  a  contagious  disease  in  the  flock  up  to  this  date, 
and  no  deaths  occurred  subsequent  to  the  ones  reported  here.  A  careful 
examination  of  these  fowls  showed  that  one  contained  bacteria  closely 
resembling  swine  plague,  and  that  in  the  other  there  was  an  extensive 
croupous  exudate  throughout  the  larynx  and  trachea,  the  specific  cause 
of  which  was  not  determined. 

Fowl  1.  This  fowl  was  sick  2  days  before  its  death.  Heart  muscle  pale  ;  in  right 
yentricle  a  mixture  of  a  pale  and  dark  gelatinous  clot.  Liver  sprinkled  with  a  few 


159 

grayish  spots,  apparently  necrosed  tissue.  Spleen  normal.  Kidneys  injected  with 
unites  and  enlarged.  Trachea  and  a-sophagus  normal.  On  cover-glass  preparations 
from  the  liver  are  minute  bodies  which  appeared  to  be  bacteria.  Tubes  of  agar 
inoculated  with  a  bit  of  the  blood  and  liver  developed  a  rich  grayish  growth  not 
distinguishable  from  an  agar  culture  of  swine-plague  bacteria, 

April  524  a  rabbit  was  inoculated  subcutaueously  with  a  very  small  quantity  of  the 
growth  from  the  blood  culture.  The  rabbit  died  in  20  hours.  Innumerable  swine* 
plague  bacteria  in  the  various  organs.  The  polar  stain  was  very  marked  in  stained 
cover-glass  preparations.  Pure  cultures  of  the  same  bacteria  were  obtained  from  the 
blood. 

April  28  two  fowls  were  inoculated  with  an  agar  culture  from  the  blood  of  fowl 
No.  1.  The  surface  growth  of  the  agar  culture  was  diluted  with  about  1  cubic  cen- 
timetre of  sterilized  bouillon.  Of  this  dilution,  fowl  a  received  0.5  cubic  centimetre 
subcutaneously  over  the  pectoral  muscle,  and  fowl  &  received  0.5  cubic  centimetre 
into  the  pectoral  musclo. 

Fowl  I  died  May  4,  At  point  of  inoculation  a  yellowish  membranous  sequestrum 
beneath  the  skin  over  an  area  about  2  inches  long  ;  beneath  this  the  pectoral  muscle 
was  necrosed  to  a  depth  of  about  one-half  inch.  The  surrouudiug  muscle  was 
sprinkled  with  punctiform  hemorrhages.  Heart  muscle  pale  ;  considerable  serum  in 
pcricardial  sac,  which  contains  also  several  small  straw-colored  coagula.  Liver 
fatty ;  somewhat  mottled, with  grayish  and  bright  red  areas.  Spleen  enlarged ;  friable. 
Kidneys  pale;  fatty.  The  mucous  membrane  of  intestines  somewhat  injected. 
(Esophagus  and  trachea  normal.  Lungs  of  a  grayish  color  ;  not  consolidated.  A  very 
few  oval  bacteria,  which  did  not  exhibit  the  polar  stain,  were  found  in  the  spleen, 
liver  and  blood.  Cultures  from  the  blood  and  liver  could  not  be  distinguished  from 
cultures  of  swine-plague  bacteria. 

Fowl  a  found  dead  May  11.  Fowl  much  emaciated.  At  the  point  of  inoculation  a 
sequestrum  about  1  inch  long  lying  beneath  the  skin ;  subjacent  muscle  reddened. 
Heart  muscle  pale.  Liver  fatty;  quite  firm.  Spleen  friable.  Kidneys  dsirk.  The 
mucous  membrane  for  a  distance  of  about  4  inches  below  duodenum  in  the  small  in- 
testine has  a  roughened  appearance,  resembling  superficial  necrosis.  A  few  oval 
germs  found  in  liver  and  blood.  An  agar  culture  from  the  liver  showed  same  charac- 
ters as  cultures  from  fowl  &. 

From  the  agar  culture  of  the  blood  of  fowl  1,  agar  and  gelatine  plate  cultures  were 
made.  The  agar  plates  developed  colonies  not  distinguishable  from  swine-plague 
colonies,  The  gelatine  plates  remained  free  from  growth.  Other  cultures  have  been 
made  on  the  various  media,  but  thus  far  no  difference  has  been  detected  between  the 
growth  of  this  germ  and  that  of  swine  plague. 

Fowl  No.  2.  This  fowl  was  not  known  to  have  been  sick.  Sternum  showed  evidence 
of  an  old  injury.  Liver  fatty.  Spleen  enlarged.  Kidneys  normal.  Mucous  mem- 
brane of  duodenum  generally  reddened,  also  sprinkled  with  minute  bright  red  dots, 
probably  injected  villi.  The  mucous  membrane  of  the  mouth  and  oesophagus  swollen, 
hypeneinic,  and  covered  with  a  thin  yellowish  very  friable  exudate.  The  follicles 
and  glands  deeply  reddened.  The  larynx  and  trachea  contained  a  yellowish,  croup- 
ous  exudate  in  the  form  of  a  tube,  easily  removable  in  sections  from  one-fouvth  to  1 
inch  in  length.  The  mucous  membrane  beneath  tke  exudate  swollen  ;  cyanosed.  It 
does  not  extend  into  the  bronchi.  Lungs  normal.  No  bacteria  were  found  in  the  liver, 
spleen  and  blood.  Cultures  made  from  these  organs  remained  clear,  Agar  plate  cul- 
tures were  made  from  the  tracheal  exudate.  There  developed  a  few  chromogenic  col- 
onies, and  about  h've  colonies  of  a  very  slender  motile  bacillus. 

Two  rabbits  inoculated  subcutaueously  with  pieces  of  the  exndate  remained  well. 

A  rabbit  inoculated  in  ear  vein  with  0.5  cubic  centimetre  of  a  bouillon  culture  of  the 
bacillus  obtained  from  the  agar  plates,  and  two  mice  inoculated  subcutaneouely  with 
the  same  culture,  remained  well, 


DESCRIPTION  OF  PLATES. 


PLATE  I: 

Lungs  of  a  healthy  pig  inflated,  viewed  from  the  left  side  ;  a,  principal  lobe  ;  &, 
ventral  lobe  ;  c,  cephalic  lobe ;  e,  apex  of  heart.    The  dotted  area  bounded 
by  the  line  xy  indicates  the  portion  usually  involved  in  disease. 
PL-VTE  II: 

The  same  lungs  viewed  from  beneath  (ventral,  diaphragmatic  surface) ;  a,  prin- 
cipal lobe;  6,  ventral  lobe ;  c,  median  or  azygos  lobe  belonging  to  the  right 
lung ;  e,  apex  of  heart.    The  dotted  area  shows  the  average  extent  of  the 
disease. 
PLATE  III: 

Lateral  view  of  right  lung  of  pig  No.  407,  outbreak  IV.     (See  p.  24).     The  hep- 

atized  regions  are  almost  completely  covered  with  a  false  membrane. 
PLATE  IV: 

The  same  lung  as  seen  from  the  ventral  surface.    A  portion  of  the  diaphragm  is 
fastened  to  it  by  means  of  exudate.    The  localization  of  the  disease  in  the 
anterior  (cephalic)  and  ventral  portions  is  well  brought  out  in  these  two 
plates. 
PLATE  V : 

Right  lung  from  case  9,  outbreak  VII  (see  p.  38),  showing  hepatization  of  portion 
of  cephalic,  ventral,  and  adjacent  principal  lobe.     Minute  necrotic  masses 
disseminated  through  the  hepatized  tissue.     On  the  left  more  recent  disease 
with  marked  interlobular  oedema. 
PLATE  VI: 

Left  lung  of  No.  275  (p.  46),  showing  extensive  pneumonia  after  the  injection  of 
culture  liquid  into  the  right  lung.     There  is  in  addition  exudative  pleuritis 
and  pericarditis. 
PLATE  VII : 

Section  of  lung  passing  through  bronchus.     In  the  principal  lobe  around  bron- 
chus the  lung  tissue  is  completely  transformed  into  firm  caseous  masses. 
From  outbreak  IV. 
PLATE  VIII: 

Fig.  1.  Section  through  one  of  the  lobes  of  a  diseased  lung  from  outbreak  IV, 
illustrative  of  the  caseation  so  frequently  encountered  in  this  outbreak. 
The  irregular  patches  of  a  homogeneous,  faintly  yellowish  tint  represent  the 
cut  surfaces  of  caseous  masses. 

Fig.  2.  A  portion  of  the  mucous  membrane  of  the  large  intestine  (outbreak  IV), 
showing  the  peculiar  isolated  masses  of  exudate  found  in  early  cases  of  this 
outbreak. 
1614 11  161 


162 

PLATE  IX: 

Fig.  I.  Collapse  of  groups  of  lobules  in  the  principal  lobe  of  a  pig's  lung.  Fre- 
quently associated  with  bronchitis  and  lung  worms. 

Fig.  2.  Broncho-pueuuiouia.  The  cut  surface  of  the  lung  tissue  shows  the 
occluded  small  air  tubes  as  yellowish  spots.  The  air  vesicles  or  alveoli 
appear  as  minute  yellowish  dots  in  groups  on  the  surface  of  the  lungs,  the 
color  being  due  to  the  cell  masses  filling  them  up.  The  exudate  plugging 
the  air  tubes  is  sometimes  firm  enough  to  be  teased  out  in  the  form  of  branch- 
ing cylinders.  This  form  of  lung  disease  is  frequently  associated  with  both 
hog  cholera  and  swine  plague,  and  may  occur  independently  of  them. 
PLATE  X: 

Heart  exposed  by  removing  pericardium.     The  surface  of  the  heart  (epicardinm) 
is  covered  with  exudation.     The  pericardium  very  much  thickened  by  exud- 
ation of  similar  character.     From  case  12,  outbreak  VII. 
PLATE  XI: 

Fig.  1.  Cover-glass  preparation  from  spleen  of  rabbit  inoculated  with  a  particle 
of  lung  tissue  from  case  15,  outbreak  IX.  Rabbit  dead  within  40  hours. 
Preparation  stained  in  alkaline  methylene  blue  and  mounted  in  Xylol  bal- 
sam. X  1,000. 

Fig.  2.  Section  from  left  lung  of  inoculated  pig  No.  275.  outbreak  VII  (see  p.  46), 
showing  Extensive  cell  infiltration  of  the  alveoli  and  small  air  tubes.  Tissue 
hardened  in  alcohol,  stained  in  alkaline  methylene  blue.  Mounted  in  bal- 
sam. X  140. 

Fig.  3.  A  portion  of  the  contents  of  an  alveolus  from  the  preceding  figure  highly 
magnified  to  show  swine-plague  bacteria.  X  1,100. 

Fig.  4.  From  the  liver  of  No.  454  inoculated  subcutaneously  with  bacteria  from 
outbreak  IX  (see  p.  74).     Intralobular  capillary  containing  a  mass  of  swine- 
plague  bacteria.     Section  prepared  and  stained  as  indicated  in  the  description 
of  the  preceding  plate.     X  1,100. 
PLATE  XII: 

Fig.  1.  a,  Surface  colonies  and  deep  colonies  of  swine-plague  bacteria  (outbreak 
IX)  on  an  agar  plate  one  week  old.  The  small,  round,  and  lenticular  bodies 
represent  the  deep  colonies,  the  larger  ones  the  surface  colonies ;  natural 
size,  b,  A  surface  colony  enlarged  17  diameters,  showing  reticulated  center, 
and  delicate  radially  striated  periphery. 

Fig.  2.  Two  deep  colonies  from  the  same  plate  enlarged  17  diameters. 

Fig.  3.  Colonies  of  swine-plague  bacteria  from  outbreak  I  (1886),  on  a  gelatine 
plate,  7  days  old.  x  60. 

Fig.  4.  Agar  tube  culture  of  swine-plague  bacteria  (from  outbreak  VIII),  about 
2  days  old.  Natural  size. 


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INDEX. 


Page. 

Abdomen  of  swine,  injection  of  swine-plague  bacteria  into 29  45 

Ag.ir-agar,  growth  of  swine-plague  bacteria  on 88 

Age  as  predisposing  to  infection 133 

Air  passages  of  domesticated  animals,  attenuated  swine-plague  bacteria  in..  109 

American  investigations  of  swine  plague,  review  of 118 

Animal  parasites  in  swine  plague 31.47, 104, 134 

A*''«ri8 , 134 

Attenuated  swine-plague  bacteria 94 

in  sporadic  cases  of  pneumonia  and  in 
septic  diseases  of  swine,  and  in  the  upper 
air  passages  of  healthy  swine,  and  other 

domesticated  animals 109 

Bacilli  closely  resembling  hog-cholera  bacilli  found  in  swine-plague  out- 
breaks   -. 77 

flacillus  coli  communis 19,78 

Bacteria  associated  with  swine  plague 15,77,80 

of  swine  plague.     (See  Swine  Plague.) 

Bacteriological  observations  in  swine  plague 11,32-84 

Bar'bone  bitfalino 143 

Billings,  F.  S.,  review  of  report  on  swine  plague 118 

Biological  characters  of  swine-plague  bacteria 85 

Bleisch  and  Fiedeler,  investigations  of  German  swine  plague  by 129 

Boiling  water  as  a  disinfectant 146 

Bollinger,  investigations  of  Wildseuche 141 

Bouillon  cultures,  advantages  of 14 

growth  of  swine-plague  bacteria  in 88 

Breed  as  predisposing  to  infection 133 

Buffalo  disease  in  Italy  resembling  swine  plague 143 

Burrill,  T.  J.,  cultures  of  swine-plague  bacteria  sent  by 124 

Carbolic  acid  as  a  disinfectant 145 

Caseation  of  the  lungs  in  swine  plagne 101 

Cats,  bacteria  in  air  passages  of,  resembling  swine  plague 152 

Cattle  and  game  affected  with  disease  resembling  swiue  plague 141 

bacteria  in  air  passages  of,  resembling  swine  plague 151 

Colonies  of  swine-plague  bacteria 87,88 

Comparison  of  bacteria  obtained  from  air  passages  of  domesticated  animals.  156 

Conclusions 149 

Conditions  which  favor  and  oppose  swine  plague 133 

Corrosive  sublimate  as  a  disinfectant 146 

Cultivation  of  swine-plague  bacteria 87 

Cultures,  how  made 12 

Digestive  tract  in   swine  plague 102 

Diphtheria  and  swine  plague  compared 117 

Distribution  of  swine-plague  bacteria 135 

163 


164 

Page. 

District  of  Columbia,  investigations  in 23, 31 

Disinfectants,  application  of 146 

for  swine-plague  bacteria 91 

Disinfection,  rules  for 145 

Dogs,  bacteria  in  air  passages  of,  resembling  those  of  swine  plague 153 

Drying  destructive  of  swine-plagne  bacteria 90 

Echinorhynchits 134 

Feeding  as  predisposing  to  swine  plague 134 

Fermentation  tube,  use  of  in  the  diagnosis  of  hog-cholera  bacilli 81 

Food  in  its  relation  to  swine  plague 137 

Fowl  cholera 114 

disease  caused  by  bacteria  resembling  those  of  swine  plague. : 158 

Fowls  inoculated  with  swine-plague  bacteria 21,77,96 

Galtier,  investigation  of  swine  disease  in  France  by 143 

Gelatine,  growth  of  swine-plague  bacteria  on '. 87 

German  investigations  of  swine  plague 125 

German  swine  plague 31,85, 122, 125 

inoculation  of  rabbits  and  pigs  with 128 

Guinea-pigs,  inoculated  with  swine-plague  bacteria 21,47,76,95 

pneumonia  and  pleuritis  in,  caused  by  bacteria  resembling  those 

of  swine  plague 158 

Hog-cholera  bacilli 34,35,39,40,41,77 

attenuated  varieties  of 77, 138 

Hog  cholera,  its  relation  to  swine  plague 138 

post-mortem  notes  in 56 

Hog  cholera  and  swine  plague    (See  Swine  Plague  and  Hog  Cholera.) 

bacteria  inoculated  together 106 

on  same  farm  bui  not  intermingled 47 

and  typhoid  fever  compared 108 

Illinois,  investigations  in 20 

Immunity  produced  in  rabbits  with  sterilized  cultures 148 

Indol  and  phenol  in  swine-plague  cultures 89 

Inoculation  of  smaller  animals 13 

small  animals  with  swine-plague  bacteria 93 

swine  with  cultures  of  swine-plagne  bacteria 21,29,45,71,97 

German  swine  plague 128 

Intestinal  lesions  in  swine  plague 98, 102, 103 

Intestines  of  swine 17 

Intra-abdominal  injection  of  swine-plague  bacteria 29,  45 

Intra-thoracic  inoculation  of  swine-plague  bacteria 21,45,  71,  74, 113, 121 

lutra- venous  inoculation  of  swine-plague  bacteria 71,75, 128 

Introductory 9 

Iowa,  investigations  in 23,28 

Jeffries,  J.  A.,  investigations  of  swine  plague  by 123 

Joint  disease  produced  by  intra-venous  injection  of  swine-plague  bacteria. ..  75 

Kitt,  investigations  of  cattle  disease  resembling  swine  plague  by* 142 

Lime  as  a  disinfectant 91, 145 

LofBer,  investigations  of  swine  plague  by 125 

Luug  disease  in  swine  plague 98 

Lungs  of  swine,  description  of 17 

injection  of  swine-plague  bacteria  into 21,29,45,71,113 

Lung  worms  associated  with  swine  plague 104, 134 

in  outbreaks  VII  and  VIII 31,47 

Malignant  oadema  bacilli  found  in  swine-plague  outbreak 80 

Maryland,  investigations  in 27 


165 

Page. 

Mercuric  chloride  as  a  disinfectant 146 

Mice  inoculated  with  swine-plague  bacteria 21,  47,  77 

Milk,  growth  of  swiue-plague  bacteria  in 89 

Moore,  Dr.  V.  A.,  report  on  the  presence  of  septic  bacteria  probably  identi- 
cal with  those  of  swine  plague,  in  the  upper  air  passages  of  domesticated 

animals  other  than  swine 151 

Morphological  characters  of  swine-plague  bacteria 85 

Necrosis  of  the  lungs  in  swine  plague 101 

New  Jersey,  investigations  in 57 

Parasites  in  their  relation  to  swine  plague 134 

Pathogenic  action  of  swine-plague  bacteria 93 

Peritonitis  in  swine 112 

Peters,  F.,  investigations  of  German  swine  plague 131 

Phenol  and  indol  in  swine-plague  cultures 89 

Pigeons  inoculated  with  swine-plague  bacteria 21,77,  96 

Plate  cultures,  limitations  of 14 

Plates,  description  of 161 

Pneumonia  in  cattle  resembling  swine  plague , 144 

guinea-pigs  following  inoculation  with  swine-plague  bacteria.  47 

man  and  swine  plague  compared 117 

rabbits  following  inoculation  with  swine-plague  bacteria  ....     94, 124 

swine  plague 98 

sporadic  cases  of 109,  111,  151 

Post-mortem  notes  in  swine  plague 24,  32,  49,  58,  69,  72,73,  74,75,76 

Practical  observations  on  the  prevention  of  swine  plague 133 

Preventive  inoculation  for  swine  plague 148 

Rabbits  inoculated  with  hog-cholera  bacilli 35,  40, 56, 79 

swine-plague  bacteria 16, 19, 21, 25, 32, 38.  39,  49, 54, 55, 56, 

60, 65, 83, 93, 111-116, 124, 127,  128 

Rabbit  septicaemia 125, 144 

Saliva  of  domesticated  animals  containing  disease  germs 109, 151 

Schweineseuche.     (See  German  swine  plague.) 

Schiitz,  investigations  of  swine  plague  by 126 

Soil,  destruction  of  swine-plague  bacteria  in 91 

Staining  of  swine-plague  bacteria 85 

Strongy lus  paradoxus  (lung  worms) 134 

Subcutaneous  inoculation  of  swine-plague  bacteria 21, 45,  71,  74, 113, 128 

Sulphuric  acid  as  a  disinfectant 146 

Swine,  injection  into  lungs  of,  with  swine-plague  bacteria 21,29,  45,71, 113 

veins  of,  with  swine-plague  bacteria 71,75, 128 

Swine  inoculated  with  hog-cholera  bacilli 80,97 

swine-plague  bacteria 21,29,45,71,97,106,113 

large  intestine  of 17 

lungs  of 17 

subcutaneous  inoculation  with  swine-plague  bacteria..  ..21,  45, 71,  74, 113, 128 

Swine  plague  and  hog  cholera  compared 105 

intermingled,  how  distinguished 14 

and  pneumonia  in  man  compared 108 

as  related  to  diseases  of  other  domesticated  animals 141 

associated  with  hog  cholera 14, 20, 23, 27, 31, 77, 82, 84, 103,  104 

bacteria,  attenuated  varieties  of 15,55,94, 138 

carried  by  young  and  old  animals 110, 1 14 

cultivation  of 87 

distribution  and  transmission  of 135 


166 

Page. 

Swine  plague  bacteria,  general  characters  of S5 

injection  into  abdomen  of  pigs 29,  45 

lungs  of  pigs 21,29,45,71,113 

veins  of  pigs 71,  75, 128 

under  skin  of  pigs 21,45,71,74,113,  128 

inoculated  into  small  animals 93 

non-motile 86 

objects  which  may  carry 145 

pathogenic  action  of. 96 

producing  phenol  and  indol  in  cultures 89 

readily  destroyed  by  various  agents 90 

caused  by  direct  infection 69 

conditions  which  may  favor  and  oppose 133 

in  Germany  ..: 125 

investigations  by  Billings,  F.  S  — 118 

Bleisch  and  Fiedeler 129 

Burrill,  T.  J 124 

Jeffries ... 123 

Loffler 125 

Peters 131 

Schiitz 126 

A               Welch  and  Clement 122 

in  District  of  Columbia 2:5, 31 

Germany 125 

Illinois 20, 124 

Iowa ,  23,28 

Maryland 27,122 

Massachusetts 123 

Missouri 82 

New  Jersey 57 

its  relation  to  hog  cholera 106, 138 

modified  by  vaccination 94 

outbreaks  of 19,20,23,27,28,31,47,57,82,84 

prevention  of. 133, 145 

preventive  inoculation  for 148 

treatment  of 146 

with  reference  to  human  disease 108 

Table  showing  difference  between  hog-cholera  and  swine-plague  bacteria  ...  92, 105 

distribution  of  hog  cholera  and  swine  plague 140 

Temperature  at  which  swine-plague  bacteria  multiply 89 

Treatment  of  swine  plague 146 

Varieties  of  hog-cholera  bacilli 138 

swine-plague  bacteria 93, 136 

Virulence  of  bacteria,  importance  of 117 

swine-plague  bacteria 135, 144 

Water,  destruction  of  swine-plague  bacteria  in 92 

Welch,  W.  H.,  and  Clement,  A.  W.,  report  on  swine  plague 122 

Whitewash  as  a  disinfectant 146 

Wildseuche « 141 


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977  mal  industry  - 
U$A2  Special  report  on 
1891  the  cause  and  pre- 
vention of  swine 


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